Not an answer, but providing more data. I am attempting to do the same thing. There is a free product out on the web called NUnit for VS. http://nunitforvs.codeplex.com/
It allows you to run NUnit code as MSTest tests in Visual Studio. I have looked at using .netSpec Exporter to convert the .trx file to html, but of course the output is NUnit and not MSTest Error format.
Here is a copy of the .trx file.
<?xml version="1.0" encoding="UTF-8"?>
<TestRun id="f27f12f3-8236-4023-bf57-83fd798a85a7" name="Guru-dev@GURU-TESTER 2010-08-03 15:41:59" runUser="GURU-TESTER\Guru-dev" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006">
<TestRunConfiguration name="Default Run Configuration" id="3ec48e45-56f0-4200-9237-7eb6947858a0">
<Deployment runDeploymentRoot="C:\Code\TestNUnit\TestTest\bin\x86\Debug\TestResults\Guru-dev_GURU-TESTER 2010-08-03 15_41_59" />
<Hosts skipUnhostableTests="false" />
<TestTypeSpecific />
</TestRunConfiguration>
<ResultSummary outcome="Warning">
<Counters total="4" executed="4" passed="4" error="0" failed="0" timeout="0" aborted="0" inconclusive="0" passedButRunAborted="0" notRunnable="0" notExecuted="0" disconnected="0" warning="0" completed="0" inProgress="0" pending="0" />
<RunInfos>
<RunInfo computerName="GURU-TESTER" outcome="Warning" timestamp="2010-08-03T15:41:59.8378367-07:00">
<Text>Warning: conflict during test run deployment: deployment item 'c:\code\testnunit\testnunit\testproject3\bin\debug\TestNUnit.exe' directly or indirectly referenced by the test container 'c:\code\testnunit\testnunit\testproject3\bin\debug\testproject3.dll' cannot be deployed to 'TestNUnit.exe' because otherwise the file 'c:\code\testnunit\testnunit\testproject3\bin\debug\TestNUnit.exe' would overwrite deployment item 'C:\Code\TestNUnit\TestTest\bin\x86\Debug\TestNUnit.exe' directly or indirectly referenced by the test container 'C:\Code\TestNUnit\TestTest\bin\x86\Debug\testtest.dll'.</Text>
</RunInfo>
</RunInfos>
</ResultSummary>
<Times creation="2010-08-03T15:41:59.3528090-07:00" queuing="2010-08-03T15:42:02.3179786-07:00" start="2010-08-03T15:42:02.6549979-07:00" finish="2010-08-03T15:42:04.6991148-07:00" />
<TestDefinitions>
<UnitTest name="ComplexTest" storage="testtest.dll" id="34d42cfe-ec64-2f64-89e4-bcd4265b4d63" xmlns="TestTest">
<Css projectStructure="" iteration="" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006" />
<Owners xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006">
<Owner name="" />
</Owners>
<Execution id="150f0d47-f5ea-42e8-be22-5b1ba882b59a" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006" />
<TestMethod codeBase="TestTest.dll" adapterTypeName="NUnitForVSTS.NUnitTest.NUnitTestAdapter, NUnitForVSTS.NUnitTest, Version=5.1.0.0, Culture=neutral, PublicKeyToken=null" className="TestTest.TestFix" name="ComplexTest" />
</UnitTest>
<UnitTest name="TestNunit" storage="testtest.dll" id="280d16b4-d78c-96ba-8710-ddb2526e1aee" xmlns="TestTest">
<Css projectStructure="" iteration="" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006" />
<Owners xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006">
<Owner name="" />
</Owners>
<Execution id="2e5fab7f-f886-4bfb-aaca-33c9dac44abe" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006" />
<TestMethod codeBase="TestTest.dll" adapterTypeName="NUnitForVSTS.NUnitTest.NUnitTestAdapter, NUnitForVSTS.NUnitTest, Version=5.1.0.0, Culture=neutral, PublicKeyToken=null" className="TestTest.TestTest" name="TestNunit" />
</UnitTest>
<UnitTest name="TypeMockTest" storage="testtest.dll" id="5e5409c4-dfe1-fa29-9ce7-b19d28cfd083" xmlns="TestTest">
<Css projectStructure="" iteration="" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006" />
<Owners xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006">
<Owner name="" />
</Owners>
<Execution id="4cb372a5-42b9-444b-85b2-fd2c85a89bb0" xmlns="http://microsoft.com/schemas/VisualStudio/TeamTest/2006" />
<TestMethod codeBase="TestTest.dll" adapterTypeName="NUnitForVSTS.NUnitTest.NUnitTestAdapter, NUnitForVSTS.NUnitTest, Version=5.1.0.0, Culture=neutral, PublicKeyToken=null" className="TestTest.TestFix" name="TypeMockTest" />
</UnitTest>
<UnitTest name="getNumTest" storage="c:\code\testnunit\testnunit\testproject3\bin\debug\testproject3.dll" id="ad820fef-b194-7297-b990-44fa4a514600">
<Css projectStructure="" iteration="" />
<Owners>
<Owner name="" />
</Owners>
<Execution id="8fa6318a-4d41-4f80-b19f-baee9f71d94b" />
<TestMethod codeBase="C:/Code/TestNUnit/TestNUnit/TestProject3/bin/Debug/TestProject3.DLL" adapterTypeName="Microsoft.VisualStudio.TestTools.TestTypes.Unit.UnitTestAdapter, Microsoft.VisualStudio.QualityTools.Tips.UnitTest.Adapter" className="TestProject3.ProgramTest, TestProject3, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="getNumTest" />
</UnitTest>
</TestDefinitions>
<TestLists>
<TestList name="Results Not in a List" id="8c84fa94-04c1-424b-9868-57a2d4851a1d" />
<TestList name="All Loaded Results" id="19431567-8539-422a-85d7-44ee4e166bda" />
</TestLists>
<TestEntries>
<TestEntry testId="ad820fef-b194-7297-b990-44fa4a514600" executionId="8fa6318a-4d41-4f80-b19f-baee9f71d94b" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d" />
<TestEntry testId="34d42cfe-ec64-2f64-89e4-bcd4265b4d63" executionId="150f0d47-f5ea-42e8-be22-5b1ba882b59a" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d" />
<TestEntry testId="5e5409c4-dfe1-fa29-9ce7-b19d28cfd083" executionId="4cb372a5-42b9-444b-85b2-fd2c85a89bb0" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d" />
<TestEntry testId="280d16b4-d78c-96ba-8710-ddb2526e1aee" executionId="2e5fab7f-f886-4bfb-aaca-33c9dac44abe" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d" />
</TestEntries>
<Results>
<UnitTestResult executionId="8fa6318a-4d41-4f80-b19f-baee9f71d94b" testId="ad820fef-b194-7297-b990-44fa4a514600" testName="getNumTest" computerName="GURU-TESTER" duration="00:00:00.0251252" startTime="2010-08-03T15:42:02.7010005-07:00" endTime="2010-08-03T15:42:03.0870226-07:00" testType="13cdc9d9-ddb5-4fa4-a97d-d965ccfc6d4b" outcome="Passed" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d">
<Output>
</Output>
</UnitTestResult>
<TestResultAggregation executionId="150f0d47-f5ea-42e8-be22-5b1ba882b59a" testId="34d42cfe-ec64-2f64-89e4-bcd4265b4d63" testName="ComplexTest" computerName="GURU-TESTER" duration="00:00:00.1660000" startTime="2010-08-03T15:42:03.8960783-07:00" endTime="2010-08-03T15:42:04.0620783-07:00" testType="d6af2cae-ad69-4f6b-94e9-14e2609e2389" outcome="Passed" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d">
</TestResultAggregation>
<TestResultAggregation executionId="4cb372a5-42b9-444b-85b2-fd2c85a89bb0" testId="5e5409c4-dfe1-fa29-9ce7-b19d28cfd083" testName="TypeMockTest" computerName="GURU-TESTER" duration="00:00:00.0050000" startTime="2010-08-03T15:42:04.0660789-07:00" endTime="2010-08-03T15:42:04.0710789-07:00" testType="d6af2cae-ad69-4f6b-94e9-14e2609e2389" outcome="Passed" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d">
</TestResultAggregation>
<TestResultAggregation executionId="2e5fab7f-f886-4bfb-aaca-33c9dac44abe" testId="280d16b4-d78c-96ba-8710-ddb2526e1aee" testName="TestNunit" computerName="GURU-TESTER" duration="00:00:00.0490000" startTime="2010-08-03T15:42:04.5571095-07:00" endTime="2010-08-03T15:42:04.6061095-07:00" testType="d6af2cae-ad69-4f6b-94e9-14e2609e2389" outcome="Passed" testListId="8c84fa94-04c1-424b-9868-57a2d4851a1d">
</TestResultAggregation>
</Results>
</TestRun>
Just wondering if some has written a xsl file for this error format?