Is it a Windows 7 pooter ? if it is, you can use WET, Windows Easy transfer to take all your stuff from one PC (Music included) over to the new pooter.
It's easy to use, just go to the start / help and type Windows Easy Transfer and follow the steps.
If it's XP, you can do the same sort of thing using FAST, Files and Settings Transfer Wizard. If you are going to a new PC running 7 (or 8) You can use WET to create an app on the USB stick that will auto run on the XP machine.
All the other advice is sound, and personally I would dump the old hard disk in a caddie, for around £5 - £10 and you've got extra storage.