Your cpu might be locked so that would explain why you cannot decrease the multiplier. That's why the 2500+ is great because it has a multiplier of 11, like the one on the 3200+. So all you have to do is raise the bus to 200mhz and you're good to go.
What kind of hsf do you have on the cpu ? If it's the stock one you should replace it with a better one. I highly suggest one of the thermalright heatsinks. (SLK-800u or 900u)
You *should* be able to get 400mhz on the FSB if you keep the multiplier at 11.5 (default), but you'll probably need to raise the voltage a little.
Basically what you do is you raise the fsb in small increments (5mhz). Then you test it by playing some games, running some benchmarks, maybe a little Prime95 or any cpu stressing software and then you raise the fsb again.
Once it becomes unstable you can raise the voltage of the cpu (VCore) a little (the next higher setting) and you retest it.
Do this until you are at the edge of the cpu/mobo/ram capacity and back off a little, that should be your max oc. I'm guessing that 11.5*200 is much below the max oc though so you should be fine.
At that point, you should run Prime95 for 24 hours. If you have no errors, you can say that your system is 100% stable. What good is an oc when you can't even use your system eh ?
To stress it more, you can run a couple of loops of 3dmark while running Prime95.
Other things to account for while ocing
- your power supply (has to be a quality one that is powerful enough)
- your ram (if you have PC3200 memory you're fine, keep the default timings, you can tweak them later to get that extra power from it). Also, if you're in Dual Channel, that might bring down your oc quite a bit, especially if they're not matched pairs. If you have corsair memory, you have to raise the DIMM voltage to 2.7V
- your motherboard: this board supports up to 400mhz on the fsb so higher than that, it's a bonus
- your cpu: again, anything higher than its default speed is a bonus.
- luck: if you're lucky, you got a good ocing chip, if not, you don't, and you can't do anything about it
- cooling: you have to monitor the temperature of the case and of the cpu. I personally want to stay below 50C under load, but below 55C is ok. Anything higher and you should look into it. Higher than 60C is unacceptable imo)