Extra storage is normally very easy.
All you need to do is take out the HDD from your other PC, there is normally 2 screws either side of the HDD and two plugs at the front.
Find a place in your compaq where your additional HDD will slide into, and use the same 2 screws either side to hold it in place. If your lucky enough, there is normally a spare power socket and socket on your IDE ribbon cable.
The only configuration you will need to do to the drive itself, it change the jumpers. If your using the socket on the ribbon cable at the very end, you will need to set your HDD to master. If your using the socket on the ribbon cable in between, set your jumper to Slave.
The configuration of which jumper is normally demonstrated on the front of your HDD. After installing your HDD, you may need to enter BIOS to pickup your HDD, but in most cases, it will pickup any new drives automatically during bootup.
RAM is a completely different matter. The development of
RAM has increased dramatically over the years, and there are many many different sizes, types and speed. If you remove the
RAM from both PC's (
RAM is quite delicate, so you will need to handle with care, try to hold the edges or use an anti-static wrist band if possible). If you can give me as much information as you can see on each chip, I will tell you if you can use them both.