I've had problems like this since my first Win 98se computer. more agony than I like to remember. Ive had to patch part of windows update, uninstall about 5 updates and change the order before thy would " stick". Then there was the famous Xp SP3 disaster , born of a Norton conflict( MS blamed Symantec and vice versa) that trashes my OS so bad I had to do a clean reinstall. I've been able to go to Google all but one and find an answer( the SP3 dodn't count the solution MS came up with was post mortem)
and one time I actually posted a solution after getting a hint from someone elses post - Yay, I was proud because I'm no techie. Has taken me up to 3 weeks to clear some of my update snafus.

I'm having PTSD!

You can always say, fuckit! back up your files, and reinstall XP. I've done it it several times. Fortunately I used to always save my program installer executables in a special folder, which helped in the process. Really wasn't that traumatic and there was a definite improvement in performance afterwards.