Tonight my computer froze and when it came back up, the screen was big and the colors were messed up, sort of like the computer was in safe mode, except I could still hear my music playing. A box came up and said:

The ati2dvag display driver has stopped working normally. Save your work and reboot to restore full display functionality.
I restarted the computer and it worked fine. About 15 mins later, it froze again and the same box came up.

What should I do? I have an IBM thinkpad T30.

Make sure you have the latest drivers.
They are available here: Graphics Drivers & Software (http://support.amd.com/us/gpudownload/Pages/index.aspx)

Also make sure you have blown the dust out from the exhausts.

I have read that Windows Defender also causes problems with older ATI drivers, so worth removing this if you are running it.