More Memory
The cheapest and easiest computer upgrade you can perfrom is a memory upgrade. The hardest part is knowing what type of memory to buy, but here the website http://crucial.com/uk/ can be a great help.
It has a piece of software that will scan your system, see what memory you are currently using and then recommend the correct memory that you should buy. You can then purchase the memory from Crucial.
Installing memory is very easy, just make sure you have discharged any static that may have built up in your body by touching a top or anything else that is earthed. The new memory then just clips into slots on the motherboard.
Of course if you are worried about doing that yourself we can fit the memory for you!