kalpik said:
Your computer will most probably accept SD ram. download CPU Z from *www.cpuid.com and check the memory tab for information about your current RAM. And definately, the performance will improve when adding extra memory!
While adding extra memory will improve the performance, there is generally a trend of diminishing returns after a particular point. The reason is that there are many parameters such as the processor speed, the processor cache, the memory (speed and amount), etc. which affect the overall speed of the computer. After one point, your memory will not be a bottleneck - the processor and other components will, and adding more memory wont improve the performance by much.
Considering that your computer has a 1 GHz processor, I dont think that anything more than 256 MB RAM will improve the performance by much. You just have to keep this in mind - what was the amount of memory that was considered to be adequate when your computer's processor was new...
If someone with 1 GHz processor recommends 512 MB RAM or more, take their advice because they know first hand...
Hope this helps,
Arun