Go buy a server with 2/4 or more SCSI disks รก 40 GB or more, Raid Array for disk-mirroring, about 1 GB Ram, one 1.6 Ghz and up or two 1.0 Ghz CPUs, 2 Ethernet ports and a tape drive. Any small/midrange server would suffice, avoid IDE HD, avoid bleeding edge hardware such PCI-X. Gigabyte, Asus, Dell, IBM, HP/Compaq and others do sell such machines, check local vendors also.
You should consider buying a 24 hour support or better and maybe a written consent that SME will run/is supported on the machine would be a good idea. The HP machine below is just an example, i am not related to HP nor do i recommend HP Servers. If you configure the ProLiant ML330 G3 to fit your needs, it comes out with 2300$, 4 hour response, 3 yr warranty, 2nd drive, tape drive, Array Controller. You can also go for ML110 or tc2120.
http://h18004.www1.hp.com/products/servers/platforms/index-tc.htmlIf your not sure what to choose, just ask.