Windows XP Media Center Edition (MCE) is a 3rd version of Widnows XP
(home/pro/MCE) (actually Tablet would be a 4th version, to complete the
list). MCE is based on XP Pro, and is mostly a superset of it but
domain based networking has been deleted.
[The explanation that follows isn't exactly technically correct, but
probably conveys the experience better than most technically correct
explanations would.]
Basically, you can think of MCE as having two different desktops, which
you can freely switch between. The first is the normal XP Pro desktop.
The second is the Media Center Desktop, which is ehshell.exe (but it
would be wrong to think of it as simply a program running under XP; you
can't move or install ehshell on just any computer running XP Pro).
The media center "desktop" was designed for a multimedia experience, and
was designed for display on a TV set to be viewed at a distance of ten
to twenty feet. It's primary function is watching and recording TV,
using the computer as a DVR (think TiVO on steroids), but it also has
tremendous music, movie and still photo capabilities (think 5,000 song
jukebox with album covers, etc.).
In order to really use MCE, you need a somewhat specialized hardware
configuration. You need an MCE approved tuner, which means that it
needs to have hardware MPEG encoding in the tuner. There are not that
many such products, for example none of the ATI "All-in-Wonder" tuner
products qualify, and only one of ATI's "TV Wonder" products qualify.
The video board is also critical, while many to qualify, most don't, and
in almost all cases different drivers are required for using a
(compatible) video card under MCE than under standard XP. Some other
system components are also far more restricted / limited in your choice
for MCE than they are for standard Windows XP.
Clearly you are having a problem, because the Media Center interface is
not coming up. Although lots of people buy the MCE OS and try to
install it on desktops and have lots of problems (you really have to
design a system to be MCE from the ground up, using only components from
the MCE HCL (hardware compatability list) or you can get into a LOT of
problems), one would expect that any system that Dell shipped with MCE
factory installed would be MCE compatible and would work. So in your
case, I'd call Dell.
To really use MCE, you need an APPROVED TV tuner (or several, MCE
supports multiple tuners; but there are not that many tuner models that
are approved) and a compatible remote control (normally, the Microsoft
remote control (about $40)). For laptops, there are a few USB 2.0
approved tuners. MCE will run without these, but the real point of
using it is lost if you don't have them.