There may be components and properties available on 2008 that are not available on 2005. This is what makes the conversion so difficult.
However if you package is simple and fairly standard then the following might help. It worked for an empty package. I created one on 2008 and then attepted to open it in 2005. I got errors (of course). So I then copied the 2008 version and opened it in a plain text editor.
I then manually edit the file
1. Change the following
<?xml version="1.0"?><DTS:Executable xmlns:DTS="www.microsoft.com/SqlServer/Dts" DTS:ExecutableType="SSIS.Package.2">
to
<?xml version="1.0"?><DTS:Executable xmlns:DTS="www.microsoft.com/SqlServer/Dts" DTS:ExecutableType="SSIS.Package.1">
2. Change the following
<DTS:Property DTS:Name="PackageFormatVersion">3</DTS:Property>
to
<DTS:Property DTS:Name="PackageFormatVersion">2</DTS:Property>
3. Remove the following:
<DTS:Property DTS:Name="LastModifiedProductVersion">10.0.1600.22</DTS:Property>
4. Change the following:
<DTS:Property DTS:Name="CreationName">SSIS.Package.2</DTS:Property>
to
<DTS:Property DTS:Name="CreationName">MSDTS.Package.1</DTS:Property>
This works for an empty package, but I can make no guarantees for any other. #
Hope this helps,
James