Hi. I am wanting to upgrade the ram on my levono thinkcentre as its slooooow as. RAM seems to be constantly 80%+ so I assume by upgrading it, i should see some benefits?

The computer is only used for web surfing and microsoft office. Specs are pretty poor. E5700 CPU, 2gb ram, and 250gb harddrive. 

I tried searching for info and had trouble finding if 4 or 8gb was the max. Also there are so many types, speeds, low voltage, buffed, etc etc and i really dont know what to get!

Using CPU-Z it gives this info for RAM: DDR3 PC3-8500F(533mhz) Samsung 1.5V

Ideally i want to upgrade to 8gb if its not overly expensive and if it is worth while doing.

Thanks in advance for any advice