Could be a number of things. Here's a checklist:
1) Have you tried cleaning the disk drive's lens? (lens cleaners are cheap and readily available at places like Best Buy)
2) How much RAM does your mac have? You should have at least 512 mb to ensure happy operation. Tho if you have 256, it shouldnt' be that slow. (it'll say how much you have if you choose "About this Mac" from the Apple menu)
3) If the cd you're trying to read is dirty or scratched, try a new cd.
4) make sure you don't have any other programs running, let the processor breathe.
5) What model of mac do you have? Some older G4s have slower cd roms. Sad truth. But still...it shouldn't take too terrible long to import a cd.
If you're prepared to buy a new drive, go out and buy an external one (preferably firewire, but at least usb 2.0) If it works out for you, there ya go. If not, you can box it up and return it. If you have a G4 tower, then you probably have a second slot in the front of your tower. If so, then go out and get a 52x cd-rom. Doesn't necessarily need to read DVD, as DVD-ROMs tend to slow the cd's read speed. (not to mention costing more)