It really depends because people's definitions of "good" are all different.
Look at my computer, in my profile. Cost me about £800, not including the mouse and mousepad, brand new in April 2008. That's a nice powerful computer which will run everything out there.
If you don't need a monitor, £500 should do you, add about £100 for a decent monitor and £60 for Windows if necessary. But, these things are flexible, it's usually possible to squeeze a few £s here and there to rbing the costs down.Could I use my current laptop as the monitor?

It's probably obvious to you.. but seeing as it has a screen I was wandering if it was possible, would be nice to knock of £300.

Also, I would be prepared to spend £800 (it would take a while to save up) and your PC specs look awesome, I think I might be nicking your PC off you

EDIT:

Also, I was just deleting things from Add/Remove Programs and it looks like I deleted the driver or thing that plays my sound, as no sound is playing and when I click on Volume Control it says there are no active mixer drivers.

Could you link me to one pl0x? You can't use the laptop as a monitor, no. Sorry.
£800 is a good amount to spend, you can get a great computer for that amount.
I'd be willing to sell mine on if you like I'm upgrading soon.

As for your driver question, what's the actual make/model of this laptop?It's a Compaq Presario C300.Not sure what OS you have but this should work: clicky.
Grab the audio drivers after selecting your OS.Thanks.

Another question:

How much would you think i'd get for this laptop if I sold it (and where could I sell it) as it could come in handy for SAVING up for a new desktop.

It's a 2 years old Compaq Presario C300 and has a weak right hinge and a jammed B button. It is running Windows XP Media CENTER SP2 it runs smoothly at most times and I guess I would WIPE it anyway if I were to sell it.

I will post pictures if you want. I'm just wondering for an estimate of how much it would buy for.Not sure how much you could get for it but not a lot.
You could try taking it to CEX if you have a store near you, or looking on Ebay for similar laptops to get an idea of what they're selling for.
I'd say £200 max. THOUGH for that, laptops depreciate very badly.Ya I got a CEX in my town.

I'll take it there if I decide to sell it, however a laptop could be handy for school and stuff.Just saying, CEX would be ABLE to give you a price for it so you'd have a ballpark figure of how much you could get for it. they don't usually give much though, so add some onto that and sell it elsewhere is my advice.
I was in the same situation as you, trying to sell my (older, but more powerful) laptop. I've decided that if I don't sell it to my friend who's considering it, I'm going to keep it because, much as I hate them, laptops are sometimes useful. If I do sell it, I'll save some of the money and buy a cheap laptop just so it's portable, something for about £100 maximum.Awesome, thanks.