Not impossible, very easy actually.
You will probably want to add another stick of ram, and a video card to this, BUT you should have plenty of cash to play with after the fact:
AMD Sempron 2800+ / 256MB DDR / 80GB HDD / DVD-ROM/CD-RW Combo / Flash Media Reader / S3 UniChrome 3D Graphics / 10/100Mbps LAN / Windows XP Home / Refurbished Desktop PC
Shop around. All else fails, you can recycle some of those old parts... I have a couple of PSUs, a stick of SDRAM memory (128mb) a normal cd rom... etc laying around if you want them...