Changing RAM will just increase performance. You want a side
effect, don't go looking for one :P
1GB stick will cost about $30 for DDR2 RAM, DDR1 RAM is much
more expensive, more than twice the price.
DDR1, DDR2 etc. refer to the "generation" of the RAM. They are
not backwards compatible, meaning DDR2 not compatible with DDR1,
DDR3 not compatible with DDR2 and vice versa because of the
different technologies in each RAM.
Before buying RAM, make sure you know which type of RAM your
computer uses. It's not uncommon for me to hear that ppl buy wrong
type, wrong form factor etc.
Speaking of form factor, there are 2 major form factors: DIMM
and SO-DIMM. DIMM, or Dual Inline Memory Module, is used for
desktops, while SO-DIMM, or Small Outline Dual Inline Memory
Module, is mainly used for laptops. SO-DIMMS are much smaller than
standard desktop RAM.
The maximum on one stick would be 8GB, though those are
prohibitively expensive. Think thousands of dollars. Maximum for
affordable memory is 2GB sticks.
DDR2-800: DDR2 technology, 800MHz RAM. Also known as
PC2-6400.
If you see things like PC2-5300, PC3200, PC3-10666, divide the
number after it by 8 and you get the clockspeed
(6400/8=800,4200/8=533,10666/8=1333)
As always, you wanna buy RAM, compare the prices. I'm buying my
new RAM today, 2x2GB OCZ Kit for about $90.