The very first thing to do is inventory the most recently installed programs and hardware. Something as innocuous as a mouse driver will cause a STOP error. Uninstall the drivers and unplug the devices, if only to gain enough stability to track down the source of the problem. Security software is another common culprit. Firewalls (Commodo 3's first release did this constantly), anti-virus and anti-spyware all use drivers that can crash the Windows kernel. Before removing your security programs:

Make as certain as possible that your system is as free of viruses, adware and malware as possible. If you don't already have them, here are some free resources:

• AVG Antivirus
• AVG Anti-Spyware
• Microsoft's RootKitRevealer
• HiJackThis (Have a tech look over your log)
• Spybot Search and Destroy

Check the Vista HCL (Hardware compatibility list, Internet Explorer only)

A few common codes/causes:

• 0x000000D1 - A.K.A. DRIVER_IRQL_NOT_LESS_OR_EQUAL Bad memory, paging file, bad drivers and damn near anything else.
• 0x0000007E - Kernel Mode Component error (driver), avgartk.sys

You may notice that the majority of STOP errors you run across are due to drivers.

For the adventurous and technically inclined, Microsoft has kindly provided instructions on reading the contents of your minidump file. (The file created when your computer crashes) If you find theirs irritating, I have my own instructions for reading the minidump.

Installing Comodo Firewall 3.0 without first disabling the built in Windows Firewall will cause Vista to blue screen (or reboot) immediately on startup or a few minutes after. (Previous installers would disable the firewall for you, this no longer appears to be the case.)