instead of using the Add-Remove Programs, it looks like from your description that you just deleted files and folders.
If your sound card is a RealTek you may have inadvertently deleted those drivers. If you don't have an install disk to put them back, try here:
I installed my old Logitech Web Cam, which wanted updated software, I went to the site and downloaded new stuff, which said I had to delete all the old bits. So I did and also the Real sound stuff that went with it, and now I can't get a sound out of my computer, have I deleted the wrong stuff, and if so, how do I get it back, its not in the recycle bin.
Win XP Pro + SP1, Intel pentium 4,