|In some cases you can borrow a cd to fix it. I assume you have xp and not 98.|
A usual suggestion is to run sfc.exe/scannow to check that install against your cd. Since you don't have a cd it might be possible to use anyone's xp to fix it. It isn't easy to run sfc.exe from a cd but there is another repair feature in xp. You have to read and follow the instructions at Microsoft. Basically you boot to a CD (best if same level like Service pack 2, has to be exact home or pro). The you sort of follow a repair but they way MS did it is confusing unless you really follow a how to. It will check and replace files but may render some programs not working.
Then get microsoft's security essentials too. I suspect that you have a virus causing this.
There are other ways to fix it too but get slightly more complex and may not work.
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