i'm looking at getting some new ram to into my desktop (it's an old, desktop, but does the job) at the moment I have around 768mb of ram

shocking i know!
but for the life of me, i can't remember what type of ram i got in it now (is it DDR or DDR2? i just don't know, its an Acer Aspire T120E-8820 if anyone can help) and i also don't know what the max amount of ram my motherboard will take.
is there somewhere i can on look within the control panel?
my main question is...does it matter what type of RAM i put in the machine? whether it be DDR or DDR 2
i see play have some good rices, wouldn't mind getting 2gb in there! it may perform slightly better