You need to downgrade the vista offered to get this price.
As usual downgrade the warranty to get this price and buy via Quidco for further cashback savings.
305-N026M2 - £587.57 or less delivered
Intel® Core 2 Duo Processor T5500 (1.66 GHz, 2 MB L2 cache, 667 MHz FSB)
Genuine Windows Vista business
14.1" Wide Screen WXGA (1280x800) TFT Display
1024MB 533MHz Dual Channel DDR2 SDRAM (2x512)
120GB (5,400rpm) Hard Drive
Fixed Internal 8X DVD+/-RW Drive including software
6 Cell, 56Whr Lithium Ion Primary Battery
56.6k V.92 Capable Internal Modem & Adapter
Intel® Pro Wireless 3945 802.11a/b/g Mini PCI Wireless LAN Card for Core 2 Duo Processors
Microsoft® Works 8.5 - English
Edit: since posting dell have altered the deal to Vista business only adding to the price.