While the operating systems are quite different, the PC and Mac have similarities when it comes to considering an upgrade or replacement.
Hard drives and random access memory, or RAM, are the easiest ways to give that old Mac a much-needed boost.
But by the time you add up the cost of new RAM, a bigger hard drive, perhaps a video card upgrade and a new processor board, you're looking at almost the cost of a new lower-end Mac like the eMac.
If you're curious or on a very tight budget, Other World Computing's www.FasterMacs.com has a roundup of acceleration cards from manufacturers such as Orange Micro, Newer Technology and PowerLogix. Those cards can replace your processor with a faster one. A warning: Processor upgrades are best left to serious hobbyists, and I wonder if they're even worth the effort.
Companies such as Crucial Technologies (www.crucial.com) and Kingston Technology (www.kingston.com) offer online help that lead you by the nose through getting the right RAM.
If you're feeling adventurous, they'll guide you through cracking open your computer and putting the chips in. It really isn't that hard, but like any adventure you need the right tools and the willingness to do it.
Hard drives are equally easy. Your best bet here is to get a guarantee from the supplier that it will take the drive back should it not work with your computer.