help mixing DDR1 memory speeds

I have been running 2 gigs of OCZ plats pc3200 in the PC in my sig for a while and wanted to try for more. I know the issues with xp32bit only taking 4gb total (including gpu memory), but I still wanted to give it a whirl and see what performance difference I can get.
Anywho, so I bought 2 gigs of Mushkin XP4000 of of SilverSinkSam and they work fine, but I can't get all four gigs to boot successfully or even POST? All the modules work fine separately and the mushkins work together and the OCZs work together, but try and add all four and I get nothing. The four diagnostic lights on my mobo (from sig) light up and the first goes out, but then it halts with three lights left on and I get a tone until I manually restart the process over.
The Mushkin is 250Mhz, the OCZ is 200Mhz. I am ok with them both running at 200 as long as I can get all four to run together.
Any insight, please let me know and thanks ahead of time.
Isaac

Put all 4 of them in. Reset the BIOS, turn ON your PC, if you get a POSt, good,.... if it doesnt POST, then nothing you can do.

Have you tried forcing 2T command rate?

I've tried resetting BIOS and command rate is already 2t. Anything else I can try?

Two things you might also consider: 1. Are they rated at the same voltage when each kind is run at stock speeds? It is not uncommon for different brands of ram to operate at different stock voltages, even those that are rated at the same frequency and timings. 2. How do the stock timings of the two pairs compare? Is one 2-3-3-3-2T while the other is 3-4-4-4-2T (just a hypothetical example)? Set both pairs at the timings which correspond to that of the slowest pair (higher timing numbers) and the voltage which is as high as that of the pair with the highest stock voltage rating. That way you are catering to the weakest member of the two pairs both with regard to timings and to voltage. Am I making any sense?

making perfect sense. I will try that when i get home. sounds like it will work better than other things i have tried.

Never tried mixing ram much but it might be worth a try to see if you can get 1 stick of each to work together and see if it's RAM not mixing or your board not liking all 4 DIMMs filled.