oh and my computer is (incase this is the cause?) Custom built

Processor: AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
Processor speed: 1.96 GHz
RAM: 4096
Opperating system: Microsoft Windows XP Professional
Video card: Radeon x700 series


PS. i have no clue what a Matroc RT.x100 render card is?