At the moment i dont have any parts.

I have £500 at the moment and im making about £200 a month towards this.

Ok i would recommend getting an e6300 core 2 duo over the pentium dual core.

What i dont quite understand about these CPU's is that the pentium 4 duo i picked out was 3.4ghz, i thought that would of been better than a 1.86 ghz?

What is the difference between the core 2 duo and the pentium dual core?

as AMD are so fond of saying...mghz isn't everything...

i have a 2.4ghz x2 AMD CPU and it's better then both of those in my opinion

Yep it depends on the architecture and rather than the mhz and the benchmarks give you the results.

As Garhar said you can go with AMD if you want (slightly cheaper, however are getting beaten at many things by the intel, have a look at the benchmarks)

the core 2 duo has a better performance ratio than the pentium d, but the pentium d's are a little more affordable. If you don't need it for heavy gaming, the pentium d should suffice.

What you have now looks good, you need a case, power supply (500watt suggested), memory (suggested 1gb), hard drive, cd/dvd drive, and video card (suggested pci-e at least 256 memory).

1gb is enough for today's standard

2gb is barely enough to run Supreme Commander with dual monitor...i run 4gb and it still 'slows down' but that's due to the fact it's still beta.