Different timings

[Lektroluv]

I accidently bought 2x1GB 6400C4 4-4-4-12 2.1V vers6.3 ddr2 ram (corsair).
I already have 2x1GB ddr2 ram in my pc (corsair), but it's 5-5-5-12 XMS6405v5.1

When I boot my pc with four slots filled with ram, my pc is very very slow.

I've bought the ram on the internet so it isn't easy to bring it back to the store (there is no 5-5-5-12 at this store)

My motherboard is a MSI P6N SLI MS-7350.

[RAM GUY]

With 4 modules I would suggest setting the memory frequency at DDR667 and set the memory Voltage to 2.0 Volts and set the NB/MCH/SPP Voltage to +.2 Volts as well and test the system with www.memtest.org. In addition, with some MB's (Mostly ASUS) you have to disable legacy USB in the bios when running any memory test.