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Dell.com has the Vostro 200 Mini Desktop with Dual-Core CPU, 2GB, 160GB & 20-inch LCD Monitor, for $484 with free shipping.
Select FREE UPGRADE FROM E207WFP 20"WFP to E228WFP Monitor [add $0]

You might want to choose Intel® Core™2 Duo Processor E4600 (2.40GHz, 2MB L2 Cache, 800FSB) [add $40]
Final Price for this deal: $484 + Free Shipping

Description:
# Intel® Pentium® Dual-Core E2160 (1.80GHz, 1MB L2 Cache, 800FSB)
# Genuine Windows Vista® Home Basic, Service Pack 1
# 1 Year Basic Limited Warranty and 1 Year NBD On-Site Service
# Dell 20 inch Widescreen E207WFP Analog Flat Panel Display
# 2GB Dual Channel DDR2 SDRAM 667MHz - 2DIMMs
# Single Drive: 16X DVD+/-RW Drive
# 160GB Serial ATA Hard Drive (7200RPM) w/DataBurst Cache™
# Intel® Graphics Media Accelerator 3100
# No Floppy Drive
# No Modem Option
# Integrated 7.1 Channel Audio
# No Pre-installed Productivity Software
# No Pre-installed Anti-Virus/Security Software