I need help

Normaly I never request for tech help, but this problem is driving me crazy and Google for once isn't much help to me. My problem is, sometimes the most random programs, whether its one I made, made by another company, or even a system app, will show this error when I close it:

The instruction at "#x########" referenced memory at "#x########". The memory could not be "written".

I replaced the numbers and letters of the memory address with # because they're different every time. According to my research, Nero burning programs, video codecs, AIM, and Internet Explorer are common apps to have this issue, but I either don't have those or they never gave me problems. Here are the problems that I heard can be the cause:

Damaged RAM or HDD (Not the problem)
Missing DLLs (Not the problem)
Java (Not the problem)
Windows' Prefetch folder (Not the problem)
A virus/adware
A program needs to be reinstalled
Windows Update (Coudln't be the problem)
Windows isn't assigning programs to memory banks correctly (most likely the problem)

If its adware, I hear thats something no antivirus program can detect.  So I'm helpless there.  If its a program that needs to be reinstalled, I might as well reinstall the entire OS which I desperately don't want to do.  My computer has been running rock solid for years, and I have no idea what could have caused this.  It could be anything.

My hardware is tested and perfectly fine, I did do registry scans, the software to my hardware is not pirated, and I never made a single update to Windows, but I never do so I'm sure thats not the problem.

I have Windows XP Pro SP2, new Opteron 180 (939), 2GB DDR RAM, a 160GB HDD and a 250GB HDD.  This shoudln't be a hardware issue though, so any help anyone could give me would be immensly appreciated.  I've searched on how to fix this for days.

The only hardware related thing to take note is I switched from a single core Athlon to the dual core Opteron.  I'm not sure if that would affect this - the problem did occur after I got the Opteron but I have no idea how soon after I got it.

Thank you very much in advance, please read all details before posting to save us all time.

OK nevermind, I found out each problem, or at least I think Ihave. After more research, I discovered that sometimes accountscan become faulty. Apparently Microsoft is aware of this but theydon't have a fix for this and the issue has been around since Windows2000.

So what I tried was I created a new account and copied all of mysettings from it and everything worked out fine except Opera lost halfit's settings. There is 1 memory issue still existing but I'llfind a way around it eventually.