i really really doubt that a legal or illegal key is going to effect the running of mirc, even when it does uses MS developed/controlled resources. MS just arent into hidden crashing because user x has an illegal key, its to prone to tampering by malicious code. Some app or virus or trojan just alteres your serial number then uninstalls itself, and kabang your windows starts acting up, and you have one hell of a time tracking it down. I still think he has either bad software/driver or bad hardware, its just that mirc is the one thing tripping it off.

Just to show how hard it is to find things...
I once had a scsi card and a network card that both were from good manurfacturers and both had well designed drivers, each worked fine sepeartely, and even 99.99999% of the time together, but if copying multiple 200+ meg files across the nextwork the odd lower nibble of a single byte in 150 to 200 million bytes of file would corrupt to zero, if the files were small ones it never happened. I never even picked it up for 2 years. I changed the net card, it went away, i changed the netcard back it came back, i changed the scsi card it went away. Soulution, just change one of the cards. Of course his problem maybe mb related which makes changing it a little harder.