Zeke - there is no need to go on ebay, if you have a BestBuy nearby. In the past two weeks they have had the following specials on Maxtor Hard drives -
40 gig for $59
80 gig for $69
120 gig for $79
The prices are after mail-in rebates. The best deal is the 120 gig, its a 7200rpm unit with an 8 meg cach. I think you pay $129 and get back $50 in a combo of instant & mail-in rebates.
If there is no Best Buy near you, you can get the same deals at BestBuy.com
The deals change each week, so check the web site. ones that are on special are marked, if you click on the "buy" button next to them it will give you the actual price.
And incidentally, unless your computer has no enternal space for it (unlikely, but emachines are bottom end, so possible), you will want to make your new drive as a seperate data drive, and keep the current drive for your OS and applications.