Problem with PCI Express1 0 with 2 0 video card

Hello,

I just bought a AMD 5770 1G which is PCI Express 2.0 but only have PCI 1.0 Express slot on my motherboard. I started run into problem when playing Starcraft 2, it will slowdown almost to halt & need to close the game. At the same time, as soon as the game starts, an message comes out saying video running out of page need to lower my graphic detail something like that. Any adivse? Thanks in advance. Below is my system detail:

ystem Model: P5W DH Deluxe
BIOS: BIOS Date: 10/22/09 13:41:07 Ver: 08.00.12
Processor: Intel(R) Core(TM)2 CPU6600 @ 2.40GHz (2 CPUs)
Memory: 3200MB RAM
Page File: 621MB used, 8818MB available
DirectX Version: DirectX 9.0c (4.09.0000.0904)