Stick the CD in and do a repair install..... It'll replace all the existing files with the originals and bring it back to day 1, as long as other things arent majorly fubar'd
If that doesn't help, save all your junk and wipe the drive, then start from scratch....
Really IS no "simple" way to clean up corrupted files, especially when you're getting Kernal errors..
Incidentally, symlcsvc (.dll/.exe ?) is part of a Norton application... Anti-Virus, or System Works, most likely..... Try uninstalling all Norton products, and see if this solves your problem, before wiping everything clean.
Norton A/V is such a pain in the ass, I wouldn't be suprised if uninstalling fixed it Just having it running it's background scan alone will slow many computers down substantially, because it's such a resource pig...
If you cant run scandisk or defrag tho, I'd just say it's time for a fresh install, after wiping the drive.
Try uninstalling anything Norton flavored, then see what happens first though...