Windows XP Problems... CMD Question

Before I speak, I would like to say a few words.
I am by no means computer illiterate, but after quite a while of digging, searching online, and tinkering, I am stumped.

I seem to have found myself it quite an odd situation...
A few weeks ago, I finally got my MyPC Windows XP SP2 desktop computer out of storage, let it warm up in my room for a day, then started it up. It refused to boot, giving me a 4-beep POST code. A little digging online, and I found a solution. (rubbing erasers on the memory sticks) After successfully booting up after the fix, I went about updating all my now outdated software.

I got to my anti-virus, and realized that after removing Avira previously, I had none. This wasn't too big of a problem at the time, because I had another computer to scan with, before I brought the files to the desktop. I tried to download and install AVG Free Edition, both from the official website and from this wonderfully handy place you have here, and I got an error about not having permission to access a registry key.

Being the only non-default administrator on my computer, this had me a little confused. I looked the problem up online and tried their solution: Manually editing just the permissions for the key via regedit. I finished and then tried the install again. No dice.

I must have a short or something in my computer, because I bumped it with my elbow by accident and it rebooted. Using this opportunity to go into Safe Mode, I tried changing the permissions again, then restarted.

I got into XP and tried the install again, failed, and started looking up solutions online, all before I noticed my theme had changed to Classic instead of XP. I pulled up the Display Properties dialog and changed it back to XP, (stupidly) ignoring the fact that the graphics were all black inside the window.

The icons, my desktop image, and the names of compressed files are all visible, everything else (Windows menus, taskbar, folder contents, title buttons, etc) is now solid black. I restarted and booted into Safe Mode to System Restore it out of this state, only to see that the default Admin account has the same problem.

A separate limited user is unaffected, but I can't do anything from that account... I thought about using RUNAS from the command prompt, but how would you access the path for the User Accounts or System Restore dialog through CMD?

I had another bout with the computer not booting right after that, only there was no POST code. After checking and re-pressing all the power supply cords into the motherboard, the computer didn't boot, but gave me a three-beep code. Taking out and reseating the four memory sticks I have in there got it to boot properly, so now I can work on it.

Anyway, I would like to know if there is a way to do one of the following:
Change a limited user to administrator via CMD (The command prompt isn't affected by the black GUI)
Run System Restore through CMD on an admin account
Run the User Account Control or System Restore on a limited account

Or anything else you think might help this situation.

Thank you for your time and consideration, I hope this can be solved quickly.

 

This might help you get to system restore:

http://support.microsoft.com/kb/304449

 

Thank you very, very much.
I didn't have to use Safe Mode, and the System Restore dialog was mostly visible. I did have to look up screenshots at http://screenshots.leeindy.com/sys_restore_restore.shtml to see which button was Next, though. XD

I sincerely appreciate the help, I never would have found it buried in MS troubleshooting/documentation pages. lol

It's restoring now, I'll post again whether or not it fixed the problem.

On a side note, does anyone have any idea why it turned black in the first place? I have no clue.

 

All right, it worked!
I see no reason why it shouldn't have, but I don't know what caused it...
I mean, all I did was change the permissions to edit the registry, not any entry in the registry itself.

Also, I don't know if this is normal, but the key, the one I edited permissions for and that AVG didn't have permission to open, it had only one value, default, and it was unopenable. Didn't have any content or options.

 

Glad you were able to get it working. I'm not sure what was going on there, but I'd like to find out what happened if you get it figured out.

 

Thanks for the info, I'll definitely try that once I get my wireless adapter working.
I'll post whether AVG installed.

Thanks for the removal tool, I have to use CCleaner a lot for that same purpose. lol

 

I ran the registry tool, and I got 173 keys detected. I removed them, and after removing all of Avira's folders from the computer, I tried installing AVG again.

I got the same error:

"Local machine: installation failed
Installation:
Error: Action failed for registry key HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows: creating registry key....
Access is denied."

I am an administrator, so I don't see how this could be happening. Editing the permissions for this key didn't work last time, and was the start of the problem I came here for...

 

Thank you very much, I probably should have looked there first.
I apologize, and I'll do that before asking elsewhere, which I probably won't have to do. lol.
Thank you very much, I believe everything has been fixed.