You probably have a malware infection.
Help with malware:
All  MS-MVP Sites.
http://aumha.org/a/parasite.htm
http://aumha.org/a/quickfix.htm
http://www.elephantboycomputers.com/page2.html#Removing_Malware
http://mvps.org/winhelp2002/unwanted.htm
http://inetexplorer.mvps.org/darnit.html
http://www.mvps.org/sramesh2k/Malware_Defence.htm

Unexplained computer behavior may be caused by deceptive software.
http://support.microsoft.com/kb/827315

So How Did I Get Infected Anyway?
For quite a few people it's by installing Messenger Plus, whose ads for
malware don't identify the malware as such and try to convince you that you
owe it to the author.  See also:
http://www.wilderssecurity.com/showthread.php?t=27971
Don't ever do a "default" install of anything.  Always choose Custom and see
what else is being carried along.  Don't install any extras you're not sure
of.

Quite a few things you can try that might help:

Have you played with the Windows Virtual Memory settings?
If so, undo your settings and let Windows handle it on it's own.

Right-click "My Computer", "Properties", "Advanced" tab. Under Performance
section, click the
"Settings" button, "Advanced" tab, under the Virtual memory section, click
the "Change" button,
and check the option, "System managed size". Click the "Set" button, click
"OK", "Apply", and
"OK" your way out.

Virtual Memory in Windows XP http://aumha.org/win5/a/xpvm.htm

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Clean out the cache files. C:\Windows\Temporary Internet Files. Click Start,
Settings,
Control Panel, Internet Options, "General" tab Look under "Temporary
Internet Files", Click
"Delete Files", check box, "Delete all offline content", "OK", "Delete
Cookies" button.

---------------------------------

Error Message: Memory Could Not Be Read...
http://support.microsoft.com/?kbid=262490

In the root directory of C:\, modify or create the config.sys file. Add the
following:

files=65
buffers=40
stacks=64,512

If the error persists, try adding this line to your System.ini file:
Scroll down to the [386Enh] Section and One space down. Hit the
Enter Key one time to create a blank line just below the [386Enh].
In the blank line, type the following:

MinSPs=6

Click Edit, Save, Edit, exit. Shut down and restart for the changes to take
effect.
(The default is 2. If required, increase increments by 2.)

---------------------------------

If nothing helped, try here: http://tinyurl.com/cl4v

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Getting the error "The memory could not be read" on right-click button:

When you right click a file or folder, you should get the context menu...
So, there might be some invalid or corrupted entires in your context menu
that is creating the
problem

Download ShellExView from here:
http://www.mvps.org/sramesh2k/slowrightclick.htm
and check what is going on in your context menu. Delete the entries which
are unwanted or
unknown.

Let me know if any of this helped you out,
Jason.