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Installing a new hard drive remains one of the most popular upgrade projects for PC users. And it's easy to see why. Today's drives are bigger than ever and bargain priced, and they offer a performance boost, as well. You'll need that extra space for the increasingly roomy OS installs and gigabyte-eating applications that are the norm these days. And don't forget graphics, audio, and video files.

If your budget is limited, you can upgrade to a 20GB drive for as little as $120; a medium-size 40GB drive will set you back $150 or thereabouts. For maximum storage space, you can invest in a 60GB or 80GB behemoth, although prices for these larger drives are in the $200-to-$300 range. If you're comfortable making the upgrade without installation software, you can save a few bucks ($10 to $30) by purchasing a bare drive.

Manufacturers offer most drives in both 5400-rpm and 7200-rpm versions. While the 5400-rpm drives are slightly less expensive than the 7200-rpm models, the latter deliver a genuine performance boost in the form of quicker access times and improved data transfers.

The newest IDE hard drives are backward-compatible with the Ultra DMA/66 interface found on most PCs made in the last few years. But most of today's drives support the Ultra DMA/100 interface (alternatively called ATA/100), which offers burst transfer speeds of up to 100MB per second. In some operations, the new interface can speed up data transfers, but the overall performance difference is not that dramatic because the bursts involve only tiny amounts of data.

Still, if you want the best performance out of your new drive, your PC must have on-board Ultra DMA/100 support. For about $40, you can buy a card that adds Ultra DMA/100 to your PC from a company like Promise. Or you can just settle for the interface that your PC uses now.

Because your new hard disk will be bigger and faster than the one your PC currently uses, plan on making the new drive your primary drive--the new home for your operating system and applications. You can attach the old drive as a secondary hard disk and use it for archives and less frequently accessed data.

All major drive makers pack software with their upgrade kits that prepares the drive for data (partitioning and formatting) and can also copy exactly what's on your current drive to the new one, helping to make the upgrade a snap.