1. system_service_exception (tdx.sys) 0x0000003b
2. pfn_list_corrupt (no file listed) 0x0000004e
Computer: Dell Dimension E521 (Desktop), with 4GB RAM. No Video Card.
OS: Win 7 Professional 64-bit. OEM version from Newegg.
Computer originally came with Vista 32-bit. BSOD's did not start until a month or so after Win 7 64-bit was installed.
Diagnosis steps: New Nvidia drivers
installed for on-board video; New Memory sticks; neither step stopped BSOD's.
Antivirus: Newest version of Avast (Free, Home edition)
Other notes: The crashes usually happen when someone is on the computer as best we can see. They are very random otherwise. Pandora gadget is often played in the background with MS Office Open, Act by Sage, Chrome, Google Talk, those are the most active running tasks. It is not on Wifi, it is on Network directly through on-board NIC.
I have attached files per instructions.
Thanks for any or all help in advance!