Here's a configuration for a few proposes business systems that will run Windows XP Pro, Office XP, and some accounting applications. It'll cost around $1500 each to build them. Please let me know if you see any problems or have any ideas that would improve it.
Intel Boxed Pentium P4 2.26 GHz 512k 533MHZ FSB Socket 478
Asus P4B533 Intel P4 533MHz DDR w/ USB 2.0 and Audio
512MB DDR PC2100 ECC DIMMs
3COM 905CX-TXM 10/100 PCI NIC
ATI Radeon 7500 64MB DDR DVI AGP
US Robotics v90/v92 56K Performance Pro Modem
WD 80GB 7200 RPM ATA 100 Hard Drive
Plextor 24 X 10 X 40 Internal ATAPI-4 CD-RW
Teac 1.44
Antec SX635 ATX Case w/ 2 additional fans
Logitech Deluxe Access 104 PS/2 Keyboard - OEM
Logitech Optical 3 Button w/ Wheel
Microsoft Windows XP Pro Full Version OEM
Microsoft Office XP SBE Small Business Edition OEM
Intel Boxed Pentium P4 2.26 GHz 512k 533MHZ FSB Socket 478
Asus P4B533 Intel P4 533MHz DDR w/ USB 2.0 and Audio
512MB DDR PC2100 ECC DIMMs
3COM 905CX-TXM 10/100 PCI NIC
ATI Radeon 7500 64MB DDR DVI AGP
US Robotics v90/v92 56K Performance Pro Modem
WD 80GB 7200 RPM ATA 100 Hard Drive
Plextor 24 X 10 X 40 Internal ATAPI-4 CD-RW
Teac 1.44
Antec SX635 ATX Case w/ 2 additional fans
Logitech Deluxe Access 104 PS/2 Keyboard - OEM
Logitech Optical 3 Button w/ Wheel
Microsoft Windows XP Pro Full Version OEM
Microsoft Office XP SBE Small Business Edition OEM