I'd slap slackware on it, software raid the two hard drives to 4 gigs mirrored, the other 6 to be ignored. Slap an ssh and ftp server on it, run samba, and put all my truly critical documents on it. Put it directly on the internet connection, run a firewall, and suddenly be able to access your most critical documents from anywhere with internet access (password protected, of course).
Should be able to handle the job with no problems (except maybe needs a 2nd ethernet card unless you actually use that modem).
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Primary
CPU: Athlon 64 X2 4400+ Mobo: Biostar N4SLI-A9 RAM: 2G Crucial (DDR400) Video: eVGA GeForce 7900 GTX (512M) Audio: HDA X-Mystique HD(s): Maxtor 300G SATA2, Samsung 400G SATA2 OS(s): WinXP x64 Pro, Vista x32 Ultimate, Gentoo x64 Monitor(s): Primary - 19" Flat Panel (1280x1024) Secondary - 19" Flat Panel (1280x1024) Tertiary - Zenith 42" Plasma TV (1024x768 res)
Many other machines... sig too short