|Whenever you install new RAM, the 1st thing you should do is test it with memtest86, memtest86+, or windows memory diagnostic.|
There's more to the error message that just IRQL_NOT_LESS_OR_EQUAL...the additional info in that message will give you a clue as to the cause. Usually it's a driver problem or memory problem. If the system had been working OK up until you upgraded the RAM, why would you suspect the wireless card?
I'm curious as to why you got 4 x 1GB rather than 2 x 2GB? And why would you get PC2-4200 (DDR2-533) rather than PC2-6400 (DDR2-800)?