I do not use windows7 (might get a check at the beta shortly), but I think the correct place will always be better taken from the registry, because of the Windows versions being localized. My own version of C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup here looks more like "C:\Documents and Settings\All Users\Menu Démarrer\Programmes\Démarrage" (from XP, of course)
-10 for programmers using hard-coded directory names (yes, some installers will create english/different language directories at installation).
-1 for Microsoft localising directory names...
Anyhow here is a snipet for this, valid for XP at least:
commonstartup.cmd
@echo off
for /F "tokens=3 delims= " %%k in ('reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders" /v "Common Startup"^| findstr /i /c:"Common Startup"') do set StartUp=%%k
echo StartUp="%StartUp%"
___Notes_____
1: Because reg.exe from Windows2000 and XP have different command arguments, maybe the W7 one has changed too so test it before set and forget.
2: To get a list of all the system directories, issue the command: reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders" and read the lines. You might want to change the "Common Startup" for something else, if things are so different with W7.
3: There is also a personal/user list within HKEY_CURRENT_USER if you want this to be usable by some users only.