|If the drive has windows 98 or ME on it you can swap it with the PC's current drive and boot up with it. But then the OS will start installing drivers for all the new hardware. That can be difficult to work through. Check my # 5 here:|
It works the same with 95, 98 and ME.
If you have XP or probably 2000, it won't boot up and will leave you at a blue screen.
The best thing in either case is probably to install the drive as a slave to the PC's existing drive. That way you'll boot up the PC with whatever OS it currently has and the drive from the old compaq will show up in My Computer and you can view and move its files and folders.
Also, if the compaq drive has XP on it and the computer you attach it to has 98 or ME, it won't see the XP drive unless it's partitioned fat32.
Obama's a 2012'er. That explains EVERYTHING..