IRQL Not Less Or Equal blue screen error

Just when I think things are back to normal with my pc, it suddenly starts to encounter an "Error_IRQL_ Not_Less_Or_Equal" blue screen error yesterday. The dreaded blue screen appears every time I turned on my modem and it got connected to the internet. According to the message contained in the blue screen my pc has encountered a fatal error and needs to shut down to protect my pc. I rebooted my pc and the error was still there. The only way to stop the error from occuring is when I did not on the modem. I then tried all sorts of tweaks to resolve the problem but to no avail. With no more options left I decided to re-install my Windows. I'm using Windows XP Home Edition on my pc and for the re-installation I chose the upgrade installation option. And thank God that worked ! No more annoying IRQL Not Less Or Equal blue screens after that. If anyone encountered the same problem as me, just do what I did and save yourself precious time and possibly a few gray hairs as well trying to find a solution to the problem.