For a number of years I have been encountering a limit in the number
of programs I can have running simultaneously in Windows.  This
problem has for years plagued both my laptop and desktop PC running
Windows XP and Windows 2000 respectively.  I wouldn't have this
problem but I have a bad habit of only closing things when I am
finished with them and don't need to be reminded to work on them,
sometimes this means I will have the same application or document open
for weeks.

I know I am hitting a limit because when I try to open something, it
won't open; but if I close something running, then try to open
something again it will open.  When I am at the limit I can't even get
a right click menu to open.

The only thing I can figure is that I am hitting a simultaneous
running process or window limit defined or hard coded somewhere in
Windows.  A good answer to my question informs me how I can raise this
limit or otherwise fix my problem without reinstalling windows or
seeking help for my aforementioned habit.

Additional Information: Sometimes when I hit the limit the 'critical
stop' sound plays, but no message pops up and no related messages are
in the 'event log'.  I have 1GB of memory, lots of free hard drive
space and let Windows manage virtual memory.  Currently I am running
an MP3 player, FTP client, organizer, outlook, adobe reader, paint,
notepad, a collection of system tray utilities and 15 Internet
Explorer windows; a total of about 77 processes according to the task
manager.

I suggest you the use of the Maxthon browser, a Tabbed Browsing
Interface that use the engine of IE, so your navigation habits will
not must be changed.
With this you will save 14 Windows.
http://www.maxthon.com/en/

You will also save a lot of system resources.

I agree with livioflores.  I've used Maxthon (formerly MyIE) for years
now and I can have as many as 100 tabs open at one time.

Thanks for the comments, I have tried tabbed browsing in the past,
FireFox and NetCaptor, but was never able to get used to it.  Perhaps
at 29 I am already set in my ways. :-(

add more ram. 1GB is nothing. add another gig of ram and youll be able
to open more windows simultaneously

Add more ram?  I thought the purpose of virtual memory was to provide
"virtually unlimited ram" to Windows, limited only by available hard
drive space.  Is my understanding wrong?

RE:  I thought the purpose of virtual memory was to provide
"virtually unlimited ram" to Windows, limited only by available hard
drive space.

Virtual memory is designed to help but it's main disadvantage is that
it is extremely slow (compared to your RAM).