... and if you would like to join in the fun, please feel free.

I like playing games on my PC, but I'm becoming aware that the specification of my graphics card (ATI Radeon 9550) isn't upto scratch for the latest games. So I've been doing a little research in order to arm myself with a little knowledge, that most dangerous of things. And I'm thinking about buying a new graphics card and installing it myself. This looks easy enough according to this video:

How To Install Or Change My Computer's Graphics Card

But the more I read, the less sure about it I get. Basically, what is perplexing me is all this stuff about AGP slots, PCI slots and PCI Express slots. How do I know which ones I've got? One website that I went to recommended upgrading my graphics card to ATI Radeon X1800 or Nvidia GeForce 7800 (or better). Fine. I can go out and buy one of these, but what if they require PCI Express slots and I've only got plain old PCI slots? What about the power supply? What about overheating?

My motherboard is an ASUS P5PE-VM, and according to another website, the specification for that is:

CPU
LGA775 socket for IntelŪPentium D/Pentium 4/Celeron CPU
Compatible with IntelŪ 05B/05A and 04B/04A processors
Support IntelŪEM64T/Hyper-Threading Technology
(note. This motherboard does not support Intel PentiumŪ Processor Extreme Edition. )
Chipset
Intel 865G
Intel ICH5
Front Side Bus
1066/800/ 533 MHz
(FSB1066 for external graphic, FSB800 for internal graphic)
Memory
Dual Channel Memory Architecture
2 x 184-pin DIMM Sockets support max. 2GB DDR400/333/266 non-ECC, unbuffered DDR SDRAM memory
VGA
IntelŪ Extreme Graphics 2
Expansion Slots
1 x AGP 8X
3 x PCI
Storage/RAID
ICH5 South Bridge:
2 x UltraDMA 100/66/33
2 x Serial ATA
USB
Max. 8 USB2.0 ports
Audio
ADI 1888 6-Channel AC'97 Audio CODEC
Audio Sensing Technology
LAN
Marvell 88E8001 GB LAN
Other ASUS Special Features
MyLogo
CrashFree BIOS2
EZ Flash
ASUS C.P.R.(CPU Parameter Recall)
Back Panel I/O Ports
1 x Parallel
1 x COM1
1 x VGA
1 x PS/2 Keyboard
1 x PS/2 Mouse
1 x 6-Channel Audio I/O
1 x RJ45
4 x USB 2.0/1.1
Internal I/O Connectors
2 x USB 2.0 connector supports additional 4 USB 2.0 ports
CPU/ Chassis FAN connectors
CD audio in connector
Front Panel Audio connector
20-pin ATX Power connector
4-pin ATX 12V Power connector
BIOS
4 Mb Flash ROM, AMI BIOS, PnP, DMI2.0, WfM2.0
Support Disc
Drivers
ASUS PC Probe II
Anti-virus software (OEM version)
ASUS LiveUpdate Utility
Accessories
1 x Serial ATA cable
1 x Serial ATA power cable (For one devices)
1 x UltraDMA 100/66 cable
1 x FDD cable
I/O shield
User's manual
Form Factor
uATX Form Factor, 9.6" x 7.6" (24.5cm x 19.3cm)
If I go out and buy a GeForce 7800 or ATI X1800, can I be sure that they'll slot right in and work straight off the bat?

Thank you for listening. BB.