http://www.pcreview.co.uk/forums/thread-261628.php
Would probably be worth a browse through
(from a google search on nv4_mini.sys)
nv4_mini.sys is what the error report was complaining about.
nv4_mini.sys is the core driver for Nvidia graphics cards, and apparently some releases were unstable, according to a quick skim through the google search results. So, I would look at downloading the latest drivers for your Nvidia card from thier website.
A search on DRIVER_IRQL_NOT_LESS_OR_EQUAL in google brought up several reports such as
http://www.tek-tips.com/viewthread.cfm?qid=308429
You may want to have a quick google on DRIVER_IRQL_NOT_LESS_OR_EQUAL
and also
nv4_mini.sys
Hopefully - you just had the bad Nvidia drivers?
Cheers
Andy