personally i do not like compaq, but this is how its done
works on any desktop*, (* never tried it on a mac, sleaves too tight)
remove HD at the back there is a set of jumper pins (6 or eight) they will be marked
SL (slave)
CS (cable select)
MA (master)
not necesarily in that order
Open receiving pc, you need to find the ide cable (flat grey one) if it has a "spare" plug you should set the jumper to SL
if there is no spare plug you have 2 choices
1) get new ide cable with 3 plugs
2) hope your pc has 2 ide "sockets"
if your pc does have 2 ide sockets (similar plug to that first ide cable is plugged into on mobo)
then you can take the hd AND ide cable from giving pc and plug it strait into 2nd ide socket (no need to move jumper, since it was set as master in giving pc)
you then find a spare power cable and plug that into the hd
fingers crossed and switch on
NOTES:
obviously do this with pc switched off, but plugged in (earth still connected)
mobo is motherboard, which is the pcb that everything connects to
power cable is yellow, red and two blacks (not in that order)
all cables / plugs will only fit one way so if it doesnt fit its wrong cable / plug or wrong way round, NEVER force any cable / plug
when you switch on go to "my computer" ( i assume winblows o/s) there you will now see drive D, you can and should format this new drive
as i said at the start, i do not like compaq, some have "built in" software that stops it seeing a 2nd hd, dont know why, they just do (but not all)
hd is secured by small screws in its side,
I take no responceability (spelt wrong i know) for your error
you may also (just for the "fun of it") consider building a pc from scratch, it is very rewarding, but to be honest parts will cost as much as new pc, but none the less it is still rewarding to diy.
you can get all parts from Police Constable world or Joe Maplin (hi de hi) or computer fair, as i also said all parts only go in one way (unless you it it with a ammer)