No, what he means by slimline is that every PCI card has a less-wider bracket than a normal PCI card. Therefore, NOT all graphics cards will work in his system.
Graphics card choices are VERY limited for slimline PCs. This is probably the best you can get for your PC, but don't expect to be playing games on Maximum with this, but it may play most games on low/medium settings. MW2 should play on high with this, as I have read in a review of this card model (EVGA edition).
ASUS Brand (no fan, large heatsink) [ame="http://www.amazon.com/PCI-Express-EN8400GS-SILENT-512MD2-LP/dp/B004I8W4UY/ref=pd_cp_e_4"]Amazon.com
: ASUS nVidia GeForce 8400GS Silent 512MB DDR2 VGA/DVI/HDMI Low Profile PCI-Express Video Card EN8400GS SILENT/DI/512MD2(LP): Electronics[/ame]
EVGA Brand with fan [ame="http://www.amazon.com/EVGA-PCI-Express-Graphics-Warranty-512-P3-1300-LR/dp/B004BQKQ8A/ref=dp_cp_ob_e_title_2"]Amazon.com
: EVGA GeForce 8400 GS 512 MB DDR3 PCI-Express 2.0 Graphics Card with 2 Year Limited Warranty 512-P3-1300-LR: Electronics[/ame]
Credit to whoever finds a better card than this that will fit slimline PCsEdited by ProdigyWolf - 8/16/11 at 4:31pm