Re: What happens if........
sfc /scannow is a system file checker. It repairs or replace windows protected files.
It will not change any setting or disturb any of your user files. It's a real handy tool to have.
If you're not running sp2 the problems you describe will pop up from time to time. SP2 corrects alot of issues. It does however add some annoying little programs you have to put up with.