Windows XP SP3 problems

my computer had gotten extremely slow, would hang up, and just wasn't working properly. I saved all of my data files to an external hard drive, and proceeded to re-install Windows XP, SP3.

I did not re-format the drive, but the thought did cross my mind. I re-installed windows, and now I am having issues trying to re-install certain programs.

1. I cannot get any Adobe program to install. Adobe reader, flash player, etc. They will download, but when they go to install, I get a message that the install failed. It asks me if I want to install manually, and when I say yes, it again fails.

2. I tried to download plugins for my Firefox. It immediately goes to Adobe and tries to install flash player, and the same as above.

3. Internet Explorer. It downloads the link, then proceeds to install, including re-booting the computer, but Internet Explorer is nowhere to be found.

i am not really sure where I should go from here. The computer is about 1/2 useful right now. It is however, much faster, boots faster, and processes faster. I just cannot run all that I want to run.

Any advice, or any place that I should start?
Thanks!

Have you tried to install the Adobe stuff in safe mode? on their website they suggest that one should try installing in safe mode in case installing in normal mode isn't working. it may also be caused by your virusscanner.
as for the flashplayer, they suggest that the windows registry might be damaged, if you follow this link, it will take you to their website, maybe it will help you solve your problems:
http://kb2.adobe.com/cps/191/tn_19166.html