System Resources is a fixed value in the memory. Upgrading memory will not increase system resources.
You will need to close down all programs that you do not need. Also when windows starts you can prevent Windows loading programs that will eat away at your memory.
Start > Run > Type: msconfig
Click ok and click startup up at the top. Remove the ticks to free up memery when windows starts compare what you gave with click here
If you run Anti virus and a firewall leave the ticks in place.
Also if you run Windows 2000 msconfig in not included but you can you use the XP msconfig. click here