If you want to build yourself then something like this should probably do although it may be overkill, 2gb Ram is to make it a bit easier when using Vista.
AMD Athlon 64 X2 Dual Core 3800+ 2.00GHz (Socket AM2) - Retail £35.99
(£42.29) £35.99
(£42.29)
Microsoft Windows Vista Home Premium 64-Bit Edition DVD - OEM - 1Pk (66I-00788) £54.99
(£64.61) £54.99
(£64.61)
Logitech Deluxe 650 Cordless Desktop Black - OEM £11.99
(£14.09) £11.99
(£14.09)
HP DVD 1035i 20x DVD±RW x12 Ram Dual Layer DVD-Writer (Black) - OEM £13.99
(£16.44) £13.99
(£16.44)
Crucial 2GB (2x1GB) DDR2 PC2-5300C5 Dual Channel Kit (CT2KIT12864AA667) £44.99
(£52.86) £44.99
(£52.86)
Antec NSK4400 Mini Tower Case - 380W SmartPower PSU £41.99
(£49.34) £41.99
(£49.34)
Abit AN-M2 Micro ATX (Socket AM2) PCI-Express DDR2 Motherboard £43.99
(£51.69) £43.99
(£51.69)
Hitachi Deskstar 7K160 NCQ 160GB SATA-II 8MB Cache - OEM £28.99
(£34.06) £28.99
(£34.06)
Sub Total : £276.92
Shipping cost assumes delivery to UK Mainland with:
City Link Parcel Next Day (Delivered Mon-Fri)
(This can be changed during checkout) Shipping : £9.95
VAT is being charged at 17.5% VAT : £50.20
Total : £337.07