to overclock your barton is to overclock your computer. your question doesn't make sense.
Since your board doesn't have a PCI/AGP lock (I'm guessing it's a VIA chipset??), you can't really overclock at all. you may be able to bump up the FSB a little bit, but it won take much for your PCI/AGP cards to malfunction.
If you want to overclock that processor, you will have to get another mobo with a PCI/AGP lock. If you want to keep your mobo, you will have to get a Mobile Barton which has unlocked multipliers (assuming your mobo has multiplier control, it may not)
I ran into a similar problem with my first socket A system. I had a gigabyte board (i forget which model) with a VIA chipset and an AthlonXP T-bred 2600+. I wanted to get into overlclocking, but my mobo and chip were not too good for it. So i bought an Abit AN7 and a AthlonXP-M 2500+ Barton (mobile XP's have unlocked mulitpliers). I was able to overclock my 1.8GHz barton to 2.4GHz (209x11.5) stable, I probably could have gone further, but I ended up moving onto an Athlon64 system instead