slow slow slow after reinstall of xp

I have a "Dell Demension 4600" (I know thats my first problem) with 512rm. 2.66GHZ. I've had to reinstall the OS. ( I got it from a friend the screwed it up. there was no system restore or drivers) He wanted his wifes contacts from outlook and then I could have to computer. I was the second person to get it. the first said he couldn't do it so he tried to reinstall windows. so I told him his wifes info was " toast". So now I nedd to install windows. I went to a Dell chat and they told me to remove 1 of the memory sticks and the dial-up modem and install windows. I would then be able to instal drivers after that. It took forever (6hrs) to install windows. I reinstalled the memory and modem and was trying to install drivers but.... the computer runs .1 miles and hour. and I mean slow! I swapped out memory with a different computer and also swapped harddrive<---2--->motherboard cables. The Hard Drive is a Western Digital 40gb. Prior to installing windows I wrote Zeros to it and installed windows on another computer and it was fine so I know it isn't the drive. Can You Help?

Also... I went to task manager and it always says CPU is 100%. different apps sucking up the memory at different times, its kinda wild in there. Usually the task manager sucking up 50-75% which seemed awfully odd. ok ball in your court! I am sending a screen shot.
Thank You For Your Time
Carmello

 

After reading another post
http://forums.majorgeeks.com/showthread.php?t=94686
I thought of something. I did get an error while installing windows (all 4 times i tried) it simply said INF could not be installed perimiter not found. As close as I remember. also there is nothing connected to the computer but the monitor, (no printer ect.). I am now running "SFC /scannow" maybe it will come up. Also when installing windows there was a 977mb partition that I couldn't delete. tried 3 times also tried to delete the other end of the partition (Lg size of drive) thinking it would come together it did not.


I was looking to see if the other post was resolved it didn't look like it was. My problem is the same except my computer does boot up. It will not take any MS updates. I originally said 6 hours or so to install windows it may have been much longer I waited 4 hours and then went to bed. I got the error in the morning and had to click enter b4 it resumed. Sorry this post so long rambling now,.....................
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