Computer works way faster with less RAM

[Yasin40]

Hi everyone

I don't understand why but my PC runs incredibly slowly with 8GB RAM. When I switch it to 6GbB (from 4x2 to 3x2) it works fine. I've tried different RAM configs (different slots, different brands, different speeds) but it makes no difference. This is really frustrating because I do want to be able to use at least 8GB. The board is Gigabyte P35 DS4 (lga 775) and should support 8gb of ddr2. I can't reflash the bios because the flash utility thinks I have the file on a floppy disk but the computer doesn't even have a floppy drive and i can't change it in the settings.

Any help is appreciated.

Thanks