Windows Vista Why was I unable to uninstall service packs?

I recently attempted to repair install Vista, but was unable to because I couldn't find a way to remove the service packs, and my disc didn't have them on it. I know I looked inside the Control Panel/Programs/View Installed Updates link, but didn't see any links to SP1 or SP2 there. I went ahead and did a reinstall anyways, and after installing SP2, I see it in the "view Installed Updates" section.

My question here is, why was I unable to see it there before? I've used system cleaners like Ccleaner and ATF, as well as Windows' own disk cleanup utility. Could they have removed certain files that are needed by Windows to uninstall a service pack? Or is there another cause? If I ever want to repair install again, I'd rather not have to go to the trouble of reinstalling from scratch.

 

Fair enough, I recall deleting files in System or System 32 folders with XP, and being told that these files were needed to uninstall updates.

OK. I will not delete these files in the future. I've written that on a virtual chalkboard 500 times.

I guess I have one more question. I've sworn off Ccleaner (it makes info on newly-installed programs to be deleted, without your telling it to at all), and ATF as well-at least until I can chain this stuff down. On Vista's Disk Cleanup, are there any files/options that you would recommend that I NOT delete--in order to uninstall these service packs, or for any other reason?

 

OK thanks.
I've also left the thumbnail unchecked, as Vista has a tough enough time displaying folder contents (if in fact there is a relation between the two). I'll be sure to also leave the setup log files unchecked as well.