Without waiting for conroe ( which giving the budget probably isn't bad advice ) I came up with the following, which will last a good time regardless of conroe

. Put in everything, the OP can tweak slightly as needed.
((edit thread extended whilst sorting the spec - so monitor won't be needed

))
CP-169-AM AMD Athlon 64 X2 Dual Core 4400+ 2.20GHz (Socket AM2) - Retail (CP-169-AM)
£284.95 £284.95
MB-144-AS Asus M2N-SLi Deluxe (Socket AM2) PCI-Express DDR2 Motherboard (MB-144-AS)
£99.95 £99.95
MY-003-PA Patriot Low Latency 2GB (2x1GB) PC5300 667MHz DDR2 Dual Channel Kit (PDC22G5300LLK) (MY-003-PA)
£139.95 £139.95
GX-047-CO Connect3D ATI Radeon X1900 XT 512MB GDDR3 AVIVO TV-Out/Dual DVI (PCI-Express) - Retail (3056) (GX-047-CO)
£234.95 £234.95
HD-002-HI Hitachi Deskstar T7K250 NCQ 250GB SATA-II 8MB Cache - OEM (0A31636) (HD-002-HI)
£52.95 £52.95
CD-032-NE NEC ND4571 16x16 DVD±RW Dual Layer LabelFlash ReWriter (Silver) - OEM (CD-032-NE)
£24.95 £24.95
SC-034-CL Creative Sound Blaster X-Fi Xtreme Music - Retail (SC-034-CL)
£64.95 £64.95
CA-038-LL Lian-Li PC-7 PLUS Silver Aluminium Midi-Tower Case (No PSU) (CA-038-LL)
£47.95 £47.95
CA-008-LL Lian Li C-01A Aluminium CD-ROM/DVD-ROM Bezel (Silver) (CA-008-LL)
£7.95 £7.95
CA-007-TG Tagan TG430-U15 430W ATX2.01 Easycon SLi Compliant Modular Silent PSU (CA-007-TG)
£46.95 £46.95
FG-024-AK Akasa AK-183-L2B Ultra Quiet 120mm Fan - 3 pin (FG-024-AK)
£9.95 £19.90
MO-010-DE Dell Ultrasharp 2007FP 20.1" Performance LCD Monitor - Midnight Grey (MO-010-DE)
£359.95 £359.95
OS-002-MS Microsoft Windows XP Professional Edition inc. SP2 - OEM - 1Pk (E85-04026) (OS-002-MS)
£79.95 £79.95
KB-014-SK Saitek PZ08AU Gamers LED Backlit Keyboard (KB-014-SK)
£24.95 £24.95
KB-060-LG Logitech MX518 Gaming-Grade Optical Mouse (KB-060-LG)
£27.95 £27.95
SP-035-LG Logitech Z-5400 THX® Certified 5.1 310 Watts Speakers - Retail (SP-035-LG)
£112.95 £112.95
Subtotal £1,631.15
Shipping (City Link Parcel Next Day (Delivered Mon-Fri)) £54.45
VAT £294.98
Total £1,980.58