I have a shuttle XPC barebone that has a DVD+/-RW Drive, AMD 4000+ CPU and 1gb of Kingston HyperX PC3200 RAM already installed. I am also going to add a 250GB Maxtor SATA 150 HD and an internal USB card reader. I will be playing counter-strike 1.6, counter-strike source, Half-Life 2 and battlefield 2 on a 19" widescreen LCD and need the best graphics card available that will run under its 240 watt power supply. Any suggestions as to what AGP graphics card to buy? Thanks.

Is it this one?
 

 
I agree you will be very limited.  
 
Have you considered getting an external USB2 CD rom kit and getting one of those GPU PSUs like the Thermaltake W0099RU 250w?

With only a 240 watt power supply it will be very close with any recent video card. Check out this power supply calculation site first and switch out the video cards till you find one under your limit.
 
http://web.aanet.com.au/SnooP/psucalc.php
 
This one should  be ok:
http://www.newegg.com/Product/Prod [...] 6814122009
(Leadtek WinFast A7600GT TDH 256MB Geforce 7600GT $179.00)
 
There are faster ATI boards but your power supply will not handle them.

 
I agree you will be very limited.  
 
Have you considered getting an external USB2 CD rom kit and getting one of those GPU PSUs like the Thermaltake W0099RU 250w?
 
 
hmm i should get one of those...

You are right, I knew it would be tight. Maybe its time for a bigger case and real power supply, to use a video card that would play his games smooth.

i am almost positive silenx came out with a power supply specifically for the shuttle htpcs, i think it was 350 or 400 watts. i would look around and google it to see what options you have. but i would try to upgrade the power supply. the 7600gt is a pretty low power consumer although, you may have luck there. Peace.

Here are some power supplies that should fit:
 
http://www.ajump.com/ajump/dept.asp?dept%5Fid=2158
 
These will give you some real options to upgrade your video card while keeping a single package. The Thermaltake W0099RU would be a cheaper and  stronger choice but would limit your portability as suggested by tipoo above.  
 
http://www.newegg.com/Product/Prod [...] 6817153037
 
The FSP Booster would also be a good choice. Its more expensive but I would trust the quality more and with its 25amps ( probably 20 amps or so continuous) it could be used later in a newer PC with a single high power video card.
 
 http://www.newegg.com/Product/Prod [...] 6817104019

Since I don't know much about the Shuttle's PSU, at best I would recommend the 7600GS which has been estimated to use about 27w (an underclocked 7600GT).
 
http://www.xbitlabs.com/articles/v [...] ise_6.html
 
A more conservative recommendation is the 7300GS which uses about 16w of power.
 
http://www.xbitlabs.com/articles/v [...] ise_7.html

I've once run my 7800gs, overclocked from 375\1200 to 475\1400 on a celeron 2ghz, with a 230w psu! The whole system was pretty stable surprisingly, although, gaming performance was a total dog crap, it scored 6800 3dmarks 2001. But a celeron isn't much of a psu demanding cpu, and that's not what happens with your athlon 4000+, you'll have a very handicaped pc in terms of performance, or you'll experience great instability problems.
Anyways, i'm not much informed about barebones psus, but as much i know, they smaller and harder to find...
GL..