Depends what yo uwant it for really. Is it for general use, surfing, light video use (like the odd downloaded video clip and maybe a DVD or two) burning/ripping CD's, and MS Word etc, or is it for graphics intensive gaming, photoshop editing/graphic design, multimedia applications etc....?

Cos thats makles a big difference on the type of hardware you need fitting to it....

Put it into perspective - I bought an 18mth old Dell off ebay for £200. It's a 2.8 P4 CPU, and stock on board graphics and sound. I upped the soundcard to a digital one, and all I use it for is web, the odd MS Office thingymibob, burning/ripping CD's and DVD's, downloading media files (video, music etc) and very light mucking about in photoshop - it's is absolutely fine with all that Monitor, also Dell, 17" TFT - cost £75. Add to that a tenner for a basic keyboard and mouse, and thats abotu £300 for a full system