What do you do for your PC clean and up to date?

Yes, these things do help. Disk Cleanup, being part of the Windows operating system, is about as well integrated as any such tool could be. It does a thorough job. Windows' Disk Defragmenter is made by the same people who make Diskeeper, an industry-leading product, and defrag time and performance gain are virtually identical to the free versions of Diskeeper. Disk Defragmenter itself doesn't do system files, but there's a freebie called PageDefrag from Sysinternals that supplements it perfectly. Unfortunately, PageDefrag doesn't work on Vista. I use Disk Defragmenter and PageDefrag whenever I install/uninstall software. I delete temp files manually, but that's not a job for everyone.

Yes, I use the disc clean up quite frequently and the defragmenter when it says it needs it! I use the computer a lot, and I can feel when it is starting to hesitate, so I just go in and clean the disc, and it freshens it up, and doesn't hurt it!