i've been looking round ebay for a good deal on a mother board and graphics card, and i'm worried that the 2 won't be compatible, what type of RAM i should also purchase. Basically i'd like to upgrade spending about £300 to £400, but i haven't got a clue what it go for.
Agreed. You really don't know what you are getting on ebay and you have no come-back if the items turn out not to work or are incompatible.
First, you have to decide what you want the computer to do. If you want to play the latest games at the fastest possible frame rate, you end up paying nearly 10 times as much as if you do a little word processing, emailing and web surfing. There are so many combinations of processor type, speed, memory, hard drive size and graphics that you have to be clear what you want to achieve before you spend anything.
These days it can almost be worth considering a laptop as your main computer, they have become so powerful.