Usually you can just plug it in, if your new comp has only one ide plug which is used for the dvd/cd it gets a bit difficult since you have to fiddle with master/slave configuration.
First thing would be to connect the harddrive to a power supply and see if it spins up and does not start smoking. Be carefull if you try that with your new comp, i usually try this with some old motherboard & old powersupply. If it starts smoking imidiatly turn off the power or the powersupply might take damage. There IS a remote chance that you get damage on the rest of the computer (which is connected to the powersupply), but the chance is pretty low.
If it spins you can probably hook it up to another computer and copy the data, only need a free ide channle to plug it in to.
There are however two things to take care off.
First if the data is valueable make sure nothing writes onto that disk. If its really important i would go as far as either not trying at all or pulling an image with linux before doing anything. When you can not see the partitions on the drive try to scan it with recovery software, sadly most recovery software requires you to pay if you want to get any of the data, some offer free versions where you can check if the software might find anything. I have good success with R-Studio.
Second, if it was a boot drive and still working windows might give you the creeps since it takes it verry badly to have 2 bootable drives. Might be good to set a system restore point on your newe system before starting the recovery action. Sometimes its no problem at all, sometimes it messes up a bit. Still much easier to retrieve the data and after that fix windows again than loosing the data.
On a final note if you recover the data from the old hard drive be happy with that, dont continue using it. I would just throw it in the "old electronics" box and never use it again, the hassle you have if it decides to quit in 5 month is not worth the gain. I usually try to throw away old (>5 years) harddrives and put the data on new ones, not worth the trouble.
cu schutt
