If you're not going to be storing a shedload of music, then a 60 G should do you fine - once I get DSL, I can see myself easily filing up half a terabyte of HD within a few years, so if you think you're going to need a lot of storage space then RAID it up. Otherwise, don't bother. Persoanlly, if you're running a home network, I'd put a 20 GB HD on every local machine and keep most of the storage space as RAID on my local server/firewall (running Linux, natch
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It's a pity you're running XP (I'd recommend 2000 over it any day, but people do so adore those shiny buttons, don't they?), but still def go for the pro version. Yes, it's even more overpriced than the home version, but the extra networking and security functionality it gives you comes in handy, esp if you're networking at home. LAN setup with the home version is reputed to be a nightmare.