advice on new computer build

[#1]

I would like to start a discussion on best computer specs for my purpose.
I want to build a new computer with a budget of circa £600 I have a tft monitor, keyboard etc so do not need to replace these I will use the new set-up for Cad drawing, video editing, photos (so a good graphics card) as well as general work.
I want to use Vista OS, most likely Ultimate, my present set up is based on a Asus A8v M/b with a sata raid C drive plus 2 other drives for videos & backup
any help would be appreciated

[#2]

The cost of the Vista license would be on top of the hardware I do connect via cable at present I also have a wireless card on the A8V but this is not working with my Netgear router at present

[#3]

What CAD are you using? Something like Peter's suggested system looks good - just check your CAD package, printer etc will work with Vista. If you are doing any solid modelling with complex assemblies then you will need lots of memory. If your are doing this commercially then consider a RAID setup so you don't rely on a single HDD, or at least make regular backups to CD/DVD.

[#4]

Thanks Guys I an now busy checking out suppliers

[#5]

I would have a look at the Intel core 2 duo cpu's even some of the cheapest core 2 chips out perform the high end AMD cpu's.  And they really perform well in video editing.  There is a lot of info out there comparing these chips and intel come out on top 99% of the time.  I am running the Intel e6600 2.4Ghz core 2 duo chip overclocked and running cool and stable @ 3.00Ghz

[#6]

Unless you buy OEM Vista (in USA) you won't have much of a budget left for hardware.  May I suggest you buy a top of the range 'Box' install UBuntu and buy you CAD  Linux software.  If you already have the software (MS OS) then just run that in the 'Wine' emulator in Ubuntu.