Having Problems with lag, and I think I may have deleted too much

Well, first to start off;

My computer is an XP and came with pre-installed programs. (if its relevant), And Ive had it for many years. Within two months of getting it, I noticed it started lagging even though it didnt have many programs on it. I turn it off frequently and reboot when I need to. Now, its been about 3 years and the lag has been elevating to an intolerable level.

Ive checked the programs, and have deleted/uninstalled ALOT. Ive even managed to delete a few system folders on accident such as "Startup" which I dont know what it is. Ive deleted my character map on accident as well. Before I decided to delete/uninstall most of my programs today, I had alot of occipied memory. Now, the computer claims that 85% of the disk space is free. I noticed it went faster. I decided to re-download AIM and it started lagging worse than ever. I know that AIM only takes up about 4.4MB And I cant understand whats going on with it.

My intentions were to delete and uninstall EVERYTHING except the programs I needed, then start over by only re-installing 3 programs I had before.

I delete cookies and history everyweek, check for spyware/hijack attempts, and even de fragment. I cant understand whats going on. I dont know a WHOLE lot about XP, because its different from what Ive BEEN using, so if you could help I would appriciate it a whole lot.

***oh yes, and before I wrap this up; Im having some trouble with my browser for IE. Its distorting images on web pages, whereas when I use Mozilla, It dosent. Ive been through all the attributes and cant seem to figure out what wrong. If you could help me with that too, I would be exstatic. ;P

Thanks a million<3

--cole.