"Doctor, will I be able to play the piano after the operation?"
"Of course."
"Wow! Great! I never took piano lessons."
"Ahem. Having your appendix out will not teach you to play the piano, Ms. Jones."
Those security patches are supposed to keep you from getting 0wned, but if you're already "slower than molasses" it may be a little late for that. You need to find out what's really wrong, not count on Mickeysoft to magically heal itself.
Okay, one exception -- I had a sick PC that got a lot better when I installed XP Service Pack 2, simply because that one includes SO MANY files it's almost like reinstalling XP from scratch. That's really the exception to the rule, though. Putting patches on a system that's currently 0wned is building on a foundation of sand.