Usually, this error isn't anything to worry about, unless your system then freezes, or you see the error multiple times.
What device is using IRQ7? My guess would be an unused device, such as a network card not connected to a network. If you can get into Linux (or XP, if you still had it installed (never wipe out a working OS!
), you could tell easily what device used which IRQ, but you may be able to see this in the BIOS device printout when your system boots.
If you can get into Linux, you could try:
cat /proc/pci | grep 'IRQ 7'