One of the new systems available from Dell this week is this.
305-D10E02 - £564 delivered or less
Intel® Pentium® D 945 Dual Core Processor (3.40GHz, 800MHz fsb, 2x2MB cache)
Genuine Windows® XP Home Edition (Does not include Operating System Re-installation CD)
1024MB Dual Channel DDR2 533MHz [2x512] Memory
320GB (7200rpm) Serial ATA Hard Drive with 8MB DataBurst cache
16X DVD+/-RW Drive
256MB nVidia GeForce 7300 Turbocache graphics card
Dell 19" Value Flat Panel (E196FP)
Integrated Audio with Dolby Digital 7.1 capability
Microsoft® Works 8 - English
Raid is available as a free upgrade for this system
320GB Serial ATA RAID 0 Stripe 2x160GB 7200rpm drives with DataBurst cache add £0.00
Another upgrade available is Intel® Core® 2 Duo® E6300 Processor (1.86GHz, 1066MHz, 2MB) add £52.88
Reduce the warranty to minimum and buy via Quidco for cashback savings.