I'm using windows XP pro on my XPS600T. Could it be they just want you to buy a new computer???

Here's What You Need to Use Windows XP Professional
PC with 300 megahertz or higher processor clock speed recommended; 233 MHz minimum required (single or dual processor system);* Intel Pentium/Celeron family, or AMD K6/Athlon/Duron family, or compatible processor recommended
128 megabytes (MB) of RAM or higher recommended (64 MB minimum supported; may limit performance and some features)
1.5 gigabytes (GB) of available hard disk space*
Super VGA (800 × 600) or higher-resolution video adapter and monitor
CD-ROM or DVD drive
Keyboard and Microsoft Mouse or compatible pointing device

Because they haven't finished testing with the final release?

Seems Dell is phasing out the 4100 series. The latest catalog that was mailed had a notation "while supplies last" in the 4100 section. I guess thats the end of the road for that chassis design as well.
This may or may not have something to do with your inquiry.
I'm waiting to see how compatible XP is with Max Payne (a new game). Max Payne requires an 800mhz Pentium & 32Mb graphics card.

Ralph,
Why should it be running better? Did you do anything to make it run better?

Since I have been running Windows XP since April in various forms on a 4100 I would suspect that it is compatable. I have not had any issues with it at all. Runs better than when I got it a year ago with Windows ME.

Ralph Caddell

Dimension 4100 800 Mhz
384 MB PC133 RAM
Dell M781S Monitor
48X CD
Ricoh MP9120A CD-R/RW/DVD
20 g Maxtor HD 7200 RPM
30 g Maxtor HD 7200 RPM
ATI All-In-Wonder 32mb
Logitech Optical Mouse Man Wheel
SB Live Value
Altec Lansing ACS-340 Speakers w/Subwoofer
Windows ME/Windows XP RC2 Dual Boot
NAV 2001
Zone Alarm Pro
No Real Player Junk