System process hogging CPU in windows xp

Hi everyone,
I am trying to fix a friends computer and it's not going well. Here's the deal, she told me she had a virus and passed it off to me. I booted into safe mode and quickly noticed a problem. the SYSTEM process is hogging the CPU, up to 99 for usage. She has a USB mouse and it's an old computer, the mouse won't work in safe mode (actually it won't work when I boot it into regular mode) so I'm having issues with using certain tools like roguekiller.

I have tried cccleaner, malwarebytes, avg free to no avail, the problem persists. Malwarebytes came up empty after a full scan, no reported problems. AVG said there was a Trojan but since the system process is still hogging the CPU the scan is taking forever to finish (it's been going for about 9 hours now on a 64 gb hard drive).

If anyone can give me any suggestions, I would greatly appreciate it. Since her computer isn't connected to the Internet I will have a hard time posting log files to any messages.

Thanks for any help you could give me.

 

Hi and welcome to MajorGeeks!

What happens when you try to connect to the internet? Is there a problem with the Internet in Safe Mode with Networking and/or Normal Mode? More details would be helpful.

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Do you have a PS/2 mouse that you can use for the time being? Why does she suspect a virus? What problems is she experiencing? I noticed you mentioned SYSTEM using 99% cpu usage, but is there anything else that makes you and her suspect a virus?