XP works exceptionally well on the Dimension 4100 model.  My suggestions would include flashing the BIOS to the most recent version and upping the RAM to at least 256 MB (512 would be much better still) prior to installing XP.  Also, you'll have much better luck perfomring a clean installation of XP to a formatted drive than you will doing an upgrade installation.  This will require backing up all critical user generated files to external media in advance, but the results will be well worth it.

If you're hesitant about trying this on your own, there are a number of places that will do the whole thing for you, for a nominal fee.  Check the Yellow Pages for "Computers - Repairs" or visit the local Best Buy or Comp USA.  If you're going to add RAM, I'd suggest getting that from either Dell or http://www.crucial.com , as some of the generic RAM sold at retail locations can be much more trouble than it's worth.  In general, it's a good idea to make all your hardware changes (along with updating the BIOS) before you change operating systems.

I took a look at Dell's BIOS upgrade information and I could not tell if it was specific for my 4100 Dimension.  Is this important or will the upgrades they have posted work for all of them? 

Barb

You need to compare what's currently on your system (available in System Setup and/or System Information) to downloads specifically for your model.  Use the Desktop button (above left), Dimension sub-link, then choose Drivers and Downloads, enter your Service Tag ID and operating system (current or anticipated new OS should work), and all available downloads will appear.  The BIOS downloads appear to be unavailable at the moment, but will hopefully be back up before too long, as someone has already sent them a nastygram requesting that they fix it.  :smileysurprised:

Update: As of 5:30 AM CDT 04/07/06, the BIOS downloads link for the 4100 is working.  The most recent one is A11, which addressed a squealing/noise problem with Creative sound cards.  If you haven't experienced this problem, you won't need A11, but you should install A10 for Windows XP. 

Message Edited by Flooby on 04-07-200606:50 AM

You seem to be very knowledgable.  I also have an IBM Thinkpad laptop that we purchased from my husbands employer.  They have ZENwork security software so the employees could not add software while the laptop was in use in the feild.  He works on location three states away from the main office.  It is not easy to get the laptop to the office to get the ZENworks software removed.  I have tried to make a recovery disk but I do not have adminstrator rights.  I am thinking of just reformating the drive (it has two partitions) and reinstalling XP.  I do not have any of the drivers for the laptop.  Will this be a problem?

Thanks for your help

Barb