How to investigate sucked up RAM

I just installed another 256MB of RAM in a PC we're using for a fileserver, for a total of 512MB. It's using Fedora Core 2.

Thing is, just doing basically nothing, most of the memory is sapped somehow, and it's not a workstation. No X windows, nothing but accepting and receiving files. So when it DOES have to do something unusual, like run GhostScript (I think it's GS that uses command like "montage" and "mogrify" right?) the system crashes.

If I do a "top", here's the top half of the screen. As you can see, there doesn't appear to be any memory intensive processes and yet 503 MB of RAM and even some swap is eaten up.

Is there some other app I can run to show a better and more detailed memory usage? Any suggestions on how I can optimize memory usage?

Thanks!!

Mem: 517132k total, 507884k used, 9248k free, 16560k buffers Swap: 257032k total, 12792k used, 244240k free, 458096k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 30293 liam 16 0 2788 876 1516 R 0.5 0.2 0:00.22 top 2546 root 15 0 8960 568 6872 S 0.1 0.1 0:31.72 nmbd 30247 liam 16 0 8420 1972 6740 S 0.1 0.4 0:00.16 sshd 1 root 16 0 1708 104 1216 S 0.0 0.0 0:09.30 init 2 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd-0 3 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events-0 4 root 5 -10 0 0 0 S 0.0 0.0 0:00.88 kblockd-0 7 root 5 -10 0 0 0 S 0.0 0.0 0:00.02 khelper 5 root 15 0 0 0 0 S 0.0 0.0 0:00.00 khubd 6 root 15 0 0 0 0 S 0.0 0.0 0:00.21 kapmd 8 root 15 0 0 0 0 S 0.0 0.0 0:18.02 pdflush 9 root 15 0 0 0 0 S 0.0 0.0 0:08.60 pdflush 11 root 15 -10 0 0 0 S 0.0 0.0 0:00.00 aio-0 10 root 15 0 0 0 0 S 0.0 0.0 0:39.37 kswapd0 123 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kseriod 162 root 15 0 0 0 0 S 0.0 0.0 0:10.61 kjournald 995 root 16 0 0 0 0 S 0.0 0.0 0:00.00 kjournald 996 root 15 0 0 0 0 S 0.0 0.0 0:00.83 kjournald