I have set up Windows Media Player to be my CD player in one room of the 
house.  This music is then distributed in every room in my house.  But I do 
not want to go to the PC room every time I want music in any room.  I would 
like a remote control that I can just hit some "play" key, and that causes 
the "play" button in WMP to play, and "stop" that causes WMP to stop.  

I have the PC connected to a stereo system that can be controlled by X10, but 
X10 cannot control PC software.

An ATI Press Release describes the Remote Wonder, a product to suit
your exact needs!

"Take Control of Your Computer with ATI's REMOTE WONDER™
Available through ATI's website (www.ati.com) for (US) $49.99, the
radio-frequency (RF) remote control provides access to all the
multimedia functions of the ATI RADEON™ series graphics cards and
other Microsoft Windows-based computer programs.
Designed for full multimedia control, the wireless REMOTE WONDER works
through walls enabling users to maintain computer access while roaming
through their house, stage, boardroom or classroom eliminating the
need to point the remote directly at the receiver."
http://www.ati.com/companyinfo/press/2002/4480.html

ATI's Remote Wonder's product page detailing product overview,
features, reviews and images
http://www.ati.com/products/pc/remotewonder/index.html

Note that this remote can only be purchased through ATI's online store
for $49.99.
http://www.ati.com/shopati/promotions/remotewonder.html

Another possible solution is the RemotePoint RF from Interlink
Electronics. It does not detail whether or not it will integrate with
Microsoft Windows Media, but it may be worth investigating.

The product page says:
"Radio frequency wireless allows worry-free control PC-based
presentations from up to 100 feet (30 meters) away. Comfortable,
reliable and easy-to-use, RemotePoint RF eliminates the "line of
sight" limitations of infrared (IR) remotes controls."
http://www.interlinkelectronics.com/products/retail/remotepointrf.htm

It can be purchased from Interlink's store for $249.00.
http://www.interlinkelec.com/cgi-local/SoftCart.exe/online-store/scstore/p-VP4810.html?L+scstore+drcw0325ff08bc08+1017893020

Or find a cheaper price from a reseller at C|Net Shopper.com
http://shopper.cnet.com/shopping/resellers/0-11045-311-5610588.html?tag=st.sh.sr.pl.pr5610588

An additional solution that may work is the PocketPoint RF from Mind
Path Technologies. This device works up to a range of 75 feet, is USB
and PS/2 compatible and runs on Microsoft Windows 95/98/ME/NT/2000. It
sells for $159 on their website and more information can be found at
http://www.mindpath.com/Products/pocketpoint.htm or on C|Net
Shopper.com at http://shopper.cnet.com/shopping/resellers/0-7085-311-6232486.html?tag=st.sh.sr.pl.pr6232486


Additional information:

ZDNet: Remote Control Devices Reviews
http://www.zdnet.com/products/stories/reviews/0,4161,2454105,00.html


Search terms used:

rf OR fm remote computer
://www.google.com/search?q=rf+OR+fm+remote+computer

He is right.  This is a product that suits my exact needs.

Thanks!

Try this Google search for a selection of remote controls:
://www.google.com/search?q=%22remote+control%22+pc

Best wishes,
mvguy

My quick answer above was incomplete. If you want to use the remote in
a different room, you need an FM remote control. Following is a link
to one example. You could set up a infrared computer remote control,
then use the following device (or one like it) to learn the codes and
transmit them through walls.
http://www.smarthome.com/8188r.html
Searching for "home automation" may provide some help in finding other
remote controls that work through walls.

Since you mentioned X10:
http://www.x10.com/products/x10_mr26a.htm

This here might be a good place to start looking at remotes in
general:
http://shopper.cnet.com/shopping/search/results/1,10214,0-1257,00.html?qt=remote+RF

You may want to look into a wireless keyboard/optical mouse
combination from Logitech:
http://reviews.zdnet.co.uk/review/31/1/315.html
Although it's a bit expensive, and the keyboard is a bit big for a
remote, it's got nice customizable one-touch buttons for media and
internet, the keyboard and mouse are both of great quality, they're
not battery hogs, and they have a pretty good range. I've been using
this set since it came out, and nothing in the way of input devices
could be handier to have, in my setup at least.

Windows Media Player may also not be the best choice of player as the
shortcuts it uses are awkward (Ctrl-P for play, etc.)

You may be better off with WinAmp (http://www.winamp.com), which has
single-key commands.

I'm big into home automation and I use a product that allows me to
control all my MP3's over my house phones (or mic's in my ceiling). 
It is Home Automated Living's Digital Music Center:

http://www.automatedliving.com/products_dmc.shtml

You can learn more about home automation on my personal website:

http://james.lipsit.com/home.htm

Take Care,

Jim Lipsit

We author software called PlayerPal.  It is a web based front-end for
Windows Media Player 9.  You can use it from a web browser on your
PC/laptop or a WiFi pocket PC (which you can get very cheap from
Dell).

I use it at home to control all my music.  It has a Google like
interface and also lists your playlists.  For details check out our
site at http://www.playerpal.com  Currently PlayerPal is free so you
can try it out.

The software needs the Microsoft web server IIS (free with Win XP Pro,
Win 2000 and Win 2003).  However, in the future it will ship with a
web server.