Could my tablet pc be infected?

winxp tab ed sp3 on thinkpad x41

I've had weird behavior on this computer forever but currently I keep having to reinstall applications [firefox 3xes this month] and some functions I can't get to work - like the on-screen keyboard and lenovo's access connections. It seems like critical files are getting corrupted altho I haven't found any of my personal files recently corrupted. At one point I couldn't open disk defrag, device manager or run chkdsk, but running system file checker fixed that - but not the access connections or on-screen keyboard.

I have avast 5 prof, malwarebytes free and sypwareblaster and use windows firewall & a router. I recently had to replace the hdd under warranty. Lenovo's toolbox and HD Tune say it's ok. Lenovo's toolbox said memory is also ok. I also ran memtest for 24 hrs to check memory and no errors were found. I keep the hdd defragged and run chkdsk monthly. I ran lenovo's software update and all the critical and important drivers were up to date - that function won't work now and won't reinstall.

I followed the pinned clean your computer post and also ran ccleaner, superantispyware and spybot s&d and 2 online scanners - bitdefender and trend micro housecall. All they found were a few tracking cookies. After running all that malware detection could my computer still be infected by something? Do I need to run a hijack this or a rootrepeal scan? Will reinstalling winxp clear any infection? Do I need to erase the drive before reinstalling? Do I only need to worry about scanning the MBR if an infection has been IDed?

I'd appreciate any help on determining what I should do at this point.

Edited November 21, 201015 yr by AnnieMS