Do I have PCI Express? + which ATI HD can I buy?

[Stankervision]

Well I've been recently having too many errors while playing Team Fortress 2, commonly because of this integrated card I've got (desktop). As a result, I wanna buy a decent Video Card, and I know to do so first I must know which extension slot I've got. I opened my CPU Case and found I've got 2 long white bars, both saying ''PCI'' at the bottom of each of them, then 1 little black bar saying ''pciex1'' at its bottom, and then a long black bar, above of it saying ''PCI Express'' but it didn't said anything about x1, x4, x16 etc...
But firstly, I want to be 100% sure I can in some way insert a PCI Express video card, so here's a screenshot of my slots:

Well in fact there are 2 white long bars (PCI), 1 short black bar (PCIe x1) and then 1 long black bar (above saying ''PCI Express)
So with this I can be sure I've got a PCIe slot for a video card? Please reply.
Oh, forgot to mention that:

My specs are:

Windows XP SP3
760MB RAM
Intel™ Pentium 4 Dual CPU 3.0Ghz
Motherboard model:

• Manufacturer & Model: IBM
• Chipset Intel i915P/i915G Rev. B1
• Southbridge Intel 82801FV (ICH6)
• LPCIO NS PC8374L

With all that above; which ATI Radeon HD 4000 Series (4350, 4550 etc...) can I buy? Please tell me, I need a 4000 Series please !

Thanks.

 

[captaincranky]

The Intel 915 "Express" chipset does indeed provide a PCI-E X 16 socket (lane) it's the socket nearest to the CPU. You can always tell PCI-E from PCI, because PCI-E goes onto the board backwards from PCI. (The little barrier strip that prevents you from plugging something in backwards is the giveaway). If you try to plug a PCI-E card into a PCI socket, the video connections will point toward the interior of the computer!

Just verify that the socket does in fact exist. Emachines released an iteration of the 915 board in which they simply deleted the PCI-E socket. I doubt that IBM is that ignorant, but it certainly won't hurt to check.

What memory sticks do you have in this machine that add up to 768MB...?

I'm not sure what video card you should buy, but I can tell you that you should probably spring for a new power supply, Intel 915 is getting on in years, and another video card would need a higther wattage PSU.