After a few weeks after first installing 11.10, my system seems to freak out, with a solid hard drive light, little to no response to input from mouse or keyboard.

Hi,

My best guess is a runaway process is rapidly using up your RAM. If you have swap space, it'll then start pushing processes from RAM to disk (which is when your hard drive goes crazy). Finally it fills swap, too, and starts killing other processes. If you have enough time, try running "ps auxw" in a terminal and see if you can find a process that has a particularly large amount of RAM (particularly the RSS column).

Best of luck!

root 1023 5.3 4.5 77620 23168 tty7 Ss+ 12:54 12:06 /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -nov
bob 1613 0.0 1.9 148200 10032 ? Sl 12:54 0:02 /usr/lib/gnome-settings-daemon/gnome-settings-daemon
bob 1628 2.0 6.2 226016 31600 ? Rl 12:54 4:38 compiz
bob 1651 0.0 4.2 165764 21608 ? Sl 12:54 0:10 nautilus -n
bob 1664 0.7 4.2 148688 21360 ? Sl 12:54 1:39 mono /usr/lib/docky/Docky.exe
bob 1752 0.2 3.1 155328 16064 ? Sl 12:54 0:30 /usr/lib/unity/unity-panel-service
bob 1842 0.1 3.2 76092 16376 ? Sl 12:55 0:19 /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon
bob 2735 3.9 15.3 458424 77900 ? Sl 16:36 0:09 /usr/lib/firefox-7.0.1/firefox

First off, Thanks much for the assist. I cut and pasted the largest RSS users? I am a neophyte to linux, so not sure what would constitute a large amount of ram, but having said that, i do believe that both times that the run away HD thing happened i was running chromium with several tabs opened and a video trying to play in one of them. I can see from the command that you had advised me too run, that the firefox browser is by far the bigger user listed here. Come to thing of it, the problem started after i had downloaded the chromium browser.
I am using a system that I hobbled together from old parts i had salvaged. An abit av8 motherboard ,radeon graphic board, 120 gig seagate HD, and only 512 meg 3200 ddr ram. Looks like I will be needing at least 2 gig ram to run linux.
The Hd is 92% empty so i can't see how the swap file would be filled even with the paltry ram. Is there a way to increase the swap file in linux, or is it set up when the drive is partitioned when ubuntu was installed?
again thanks for your help.

OH, i'd forgot AMD64 3200+ cpu. Odd thing is, I had always thought that Linux was less demanding on hardware. Leaner and less bloated then Windows. Less a resource hog. Go figure.

Okay, I goggled the question about finding swap file size, used the free command and got:
             total used free shared buffers cached
Mem: 507252 486236 21016 0 14480 130836
-/+ buffers/cache: 340920 166332
Swap: 1028460 149056 879404
So i Have a 1 gig swap. I suppose that it is possible that the swap, got swamped, so say to say. What say I increase it to 2 gig's? until I procure the new ram? DO you think that would fix the problem short term.
Once more ,thanks.
PS sorry about all of the verbiage, I had 4 hours sleep and ingested 2 pots of coffee.

There's nothing unusually large there, so I'm guessing it's running fine now. While 512MB should be enough for light use, playing video in a browser with multiple windows open is probably too much.

The problem with swap in this situation can be that moments after something is swapped out it needs to be swapped back in again to respond to some input. This can happen in a near-continuous loop, leading to the thrashing you're seeing.

You can type "free" to see the available memory and swap space. Swap space is generally fixed in size, although you can add to it if you really need to, but I doubt it to be honest.

If you like, you could try running this command:
    watch -n 1 'ps auxw | sort -rn -k 6'
which will list the processes, sorted by memory usage, once per second. While you have that running try watching a video in Chromium and see if it jumps to the top of the list.

Could test your RAM from Grub. Hod SHIFT at boot and select the memtest option. Let it run a while, This is good:
http://www.memtest.org/pics/amd64-big.gif

This is bad:
http://www.mynetnuke.com/Portals/28/images/Articles/MemtestMNN.jpg

Memory is good checked already. But thanks.