i agree with bastieeeh. if you never experienced a memory shortage on your system with 1gb then you better leave it at that and better invest your money in a faster cpu, a faster graphics card or some faster hard disks (if you ever saw your operating system boot from a 15k-scsi-disk or even a couple of them in raid-0, you know what i mean...
). the performance you will gain from that will be much more noticable...
just watch your memory usage through the task manager. if the page file usage goes never above 800-900mb then you will be fine with 1gb and your system will not run any faster with 2 and under some circumstances, wich i described above, it could be even slower...
@overkill:
shure you can use sandra to bench the throughput of your memory and shure you get some nice numbers, but all i whould say is, that under some circumstances your system may be even slower with 2gb ram instead of 1. maybe you have a motherboard wich deals great with 4 banks of ram. most systems/chipsets, especially older ones, cannot handle more than 6 banks (and i mean banks, not slots!) of unbuffered ram. there are some benchmarks and reports out in the internet, try searching if you don't beleave me...
and in case of the bounce buffer mechanism i mentioned before: this effect is only noticable if some device drivers do some dma-access or something. this effect is not noticable in sandra, but shure it is if you run some real applications wich deal with your hardware through the drivers...
--breit
edit: i won't post any links here, but maybe you try searching google with "2gb ram slower"...