yeah you just want a normal internal hard drive exactly as you have linked

how many mp3s you likely to accomadate!? 120gb will hold 24,000 mp3s roughly! that should be more than enough!

save money on the size and go for one with a faster read time (in ms) and a bigger cache (in MB)

something like this one would be good 3rd one down

or

3rd down again

that will just sit inside your case as normal, all the necessary connections will be there and it will appear in My Computer as another hdd