Phoenix Firstbios Update

[geo791]

I have an old IBM ThinkCentre 8189F1U desktop which has an IBM FRU PN 13R8926 mb and a Phoenix Firstbios 2AKT51AUS BIOS. The OS is Windows 7 Enterprise 32-bit and has an nVidia 6200 video card. The system was constantly accessing the hd and was slow with just 2GB of installed memory. I purchased four new sticks of 1GB memory to fill the four slots. The mb documentation states the board will support 4GB of memory. After replacing the four sticks of 512k memory with four sticks of 1GB memory, the BIOS only detects 2.3GB. Windows 7 shows 4GB installed but only 2.3GB available. Could this be corrected with a BIOS update? The current BIOS date is 7/6/2005. I have searched online for hours but have not been able to locate a BIOS update. I have found some sites that say they have an update but they want $29 to subscribe to their service before I could get it. That's not going to happen. Would appreciate any comments or ideas on this issue.

[geo791]

Yes, I have searched through their site for BIOS updates but none can be found for my old IBM ThinkCentre.