Sorry, forgot you had already been to the malware area.
If the memory diags don't show anything, I would then try a hard drive diagnostic. If you don't know the manufacture or your hard dive you can usually get that info from the Disk Drives area of Device Manager (
Start then
Run, type
devmgmt.msc and press
Enter). If not you'll have to remove the drive to look at it. Once you have that information go to their web site and download the drive utility and see what it says about the hard drive. It will be an .iso file you create a bootable CD from.
One last suggestion for now. Run
chkdsk /r to see if there is a file system problem. Click on
Start then
Run, type
chkdsk c: /r and press
Enter. You will see this:
The type of the file system is NTFS.
Cannot lock current drive.
Chkdsk cannot run because the volume is in use by another
process. Would you like to schedule this volume to be
checked the next time the system restarts? (Y/N)
reply Y then reboot.
If that doesn't run or complete for some reason, try from the Recovery Console. You are going to have to get into BIOS Setup on your computer to set the CD/DVD drive as the first bootable device, so you can then boot your XP CD.
How you do this varies with each manufacturer. Normally you press F1, F2, F10 or Del when you see the manufacturers logo. Often there is a clue somewhere on the screen when you boot normally telling you what key to press. Some computers (most newer ones) have a key you can press (often F12) to bring up the Boot Menu from where you can select the CD/DVD drive to boot from.
If you don't have an XP CD, download and create a bootable CD from the .iso file
XP Recovery Console
You don't burn the iso file itself to CD., you create a CD from the iso file using your CD burning software. There is a good freeware burner called
ImgBurn which will
do this.
Boot the CD and at the first opportunity, enter
R to start the Recovery Console.
Next, choose which XP installation you want to login to. Normally this will be 1.
Lastly you will be asked for the Administrator password. Just press the Enter key as the Administrator does not have a password (unless you gave it one, then you would enter it).
From the command prompt, enter:
chkdsk c: /r
Allow it to complete undisturbed. It can take an hour or more depending on the size of the hard drive.
Remove the CD, type exit and the computer will reboot.