Trying to build a single purpose system

[johnthedoctor]

Hi, didn't realise how out of date I was until coming here. Been happy with this old AMD 400 I built, does the job and is reliable, but now I need to upgrade so the system is optimised for trading on www.Betfair.com
Bit of a dummy with software, but am OK putting hardware together.
What I'm looking for is:

1) a rock solid system for accessing just the one site, using privoxy to give me a 0.5 sec refresh rate. Hopefully using a proven mobo I can get from ebay.
2) Dual monitors, be great if privoxy was only active on one of them, but that might be wishful thinking.
3) System will have Snagit or similar running in the background and storing the screen vid onto the hard drive for burning later.
4) Whatever card gives the best perfomance for ADSL, no proper cable here yet.

I'll go dual boot if there is no chance of a virus getting from one to the other, otherwise I'll just swap drives daily.
As it's just the one site, anything simple I can do to stop any intrusions from elsewhere?

Thanks.

[BipolarBill]

Are you planning on building this yourself? Would it be the first time?

Maybe we should start with motherboard, CPU and RAM:

http://www.newegg.com/app/ViewProductDesc.asp?description=13-130-446&depa=0

http://www.newegg.com/app/ViewProductDesc.asp?description=19-116-157&depa=0

http://www.newegg.com/app/ViewProductDesc.asp?description=20-141-424&depa=0

If you need independent displays, you're probably best off with a dedicated dual-display card:

http://www.newegg.com/app/ViewProductDesc.asp?description=14-106-143&depa=0

You cannot game with that though.

As far as firewalls go, you can get a $50 router if you have DSL/Cable or you can just use this:

http://smb.sygate.com/products/spf_standard.htm