Welcome
This is what we do
Download and run a full scan with Malwarebytes. Make sure it is updated and you make the full scan.
If negative test your memory.
Guide to using Memtest86+ - Geeks to Go Forums
If those tests are negative, right click on the bottom task bar. Bring up task manager go to process tab and then click on memory to bring up to the top the heavy users, now give us a screen shot.

Memory or hard drive space?

I used to have an m8000n. According to my search it's 8 GB max memory can be installed on that machine. Also it would be helpful to fill in all the specs. When I bought m8000n it came with XP SP2 installed, not Vista. So obviously we can't just go by the standard HP specs.

Other than that I would follow Richc's advice. Malwarebytes often catches stuff that regular av misses.

I use WinDirStat myself, but if I'm not mistaken, on 64 bit systems it will be subject to directory redirection. Just thought I'd mention it. I used it on my 64 bit system too. But for diagnostic it may be better to use a native 64 bit utility.

It runs "perfectly" but since it was written in 2007 I don't think they made the API calls to disable folder redirection. Otherwise if it's a 32 bit app, the SysWow64 is going to redirect accesses to some system folders. For example C:\Windows\System32 accesses are redirected to C:\Windows\SysWow64. It doesn't matter really for normal use to see which folders you left too many videos in. But if the malware by chance is 64 bit then it might be overloading the System32 folder. You won't know that if you measure the size with a 32 bit app since you'll be actually measuring the file usage in SysWow64.

Maybe a bit unlikely, but for diagnostic purposes I think it's safer to use a native 64 bit utility to actually see what's what.

Also I'd advise using some malware scan from a boot CD. Running something from inside the account that works might not detect the malware that seems to be in the kid's account. Makes sense as kids are usually less cautious about surfing. Better to scan the whole drive from an isolated boot CD OS. For m8000n the vanilla Sata disk drivers on a boot CD should be fine.

Originally Posted by MilesAhead

Also I'd advise using some malware scan from a boot CD. Running something from inside the account that works might not detect the malware that seems to be in the kid's account. Makes sense as kids are usually less cautious about surfing. Better to scan the whole drive from an isolated boot CD OS. For m8000n the vanilla Sata disk drivers on a boot CD should be fine.

Excellent suggestion. It's the only surefire way to be certain that the malware isn't running upon boot up.