To expand on what rpggamergirl suggested, you could to export an existing key from a machine with the entry you want...and then just remove the entries that you don't want.
The nice thing about XP is that you can also do this from a command line with REG.EXE
Example, if I wanted FILE.EXE to load on startup, I would run the following:
reg add hklm\software\microsoft\windows\currentversion\run /v MyStartupApp /d "C:\PathToFile\File.exe" /F
The /F at the end says to overwrite it if it's already there - if there's no chance it would be, then the /F is not needed...
You can easily add that one line to a batch file/login script or the like to get it to automatically add...