Reinstalling WinXP Service Pack 2

I am planning to reinstall SP2 as some of the ie and system files got
corrupted.
I made this decision after trying to uninstall ie7 beta which made my ie
corrupted and chm/help files
are not working.

I have installed few patches after installing SP2 like Hotfixes,alt+tab
controller,clear type font
etc..

Now please advice me on the following
1.Can I reinstall SP2 without unistalling it or any of the patches?
2.Will it create system instability?
3.Can ie and chm related system files alone can be restored?I am saying this
b'caz i couldnt able to unistall ie7 to get back to ie6 or reinstall them
again with ie7 rc1
--
Guhan