Windows 7 (64 bit) random crashes and lockups. Please help me troubleshoot the problem

Solution 1:

Using BlueScreenView, here is the break-down of drivers that seem to have caused the crash :

athrxusb.sys : 11 crashes (Atheros USB WiFi driver)
ntoskrnl.exe : 3 crashes
USBPORT.SYS : 1 crash
atikmpag.sys : 1 crash
Ntfs.sys : 1 crash

The majority of the crashes seem to be caused by the Atheros USB WiFi driver, where your driver dates from July 29, 2008.

I would first try to work for some time without connecting the Atheros WiFi, to see whether the crashes stop arriving.

Once it is verified that the Atheros WiFi is the cause, try to find a newer driver on the Atheros site. If you can't, then get yourself another WiFi device.

Solution 2:

My next step would be to stress test the CPU and see if anything falls over.