Does CompUSA guarantee compatibility with your particular machine (whatever it might be - we don't know)?
If not, it's your risk. Make sure that you have a no-cost return for refund ability. It's basic generic RAM.
If you're talking about a PowerBook G4 1,0 - 1.33 Aluminum, or an iMac G5 rev A, then forget it, the chances of generic RAM being compatible in thise machines is slender.