Help with win XP

About half a year ago i bought a new computer. So far so good. IT was running smoothly until someday i got a virus and had to format. Did format and installed xp pro. Now these are the errors that occured after installing and rebooting: cli.exe wont start, says that it cant find a version of the runtime to run it.
The weird thing is, I already had installed .net framework 2.0 but it still says that it couldnt find it. And more: on startup tray icons like Steam, MSN, Sound and etc are not present and i have to start them manually. Another thing is that, it wont read game discs or wont launch games at all. So i formated yesterday and today it gave me the same error, but the weird thing is that the errors came when i went to my other old computer which is connected to the same router as the computer that is getting these weird errors. Because format c doesent work, im running out of ideas what to do next.

Thanks in advance.

Thanks for the info. I think before another format i will scan the older computer for viruses.