Well essentially both people are correct. You have to up your FSB to technically overclock it, but to stabilize it you have to up your voltage..see what I mean? When you're pumping more power and speed through the chip it's going to need that extra power.
How much are your upping your FSB By?
By the way take these things into consideration:
A) When you up your FSB your OC'ing your entire system. You need to have the option to lock your AGP Bus at 66MHz which will automatically lock your PCI Bus at 33 which is ESSENTIAL in Overclocking
B) Also, your RAM becomes overclocked when you raise the FSB because like the AGP the RAM's speed is determined by whatever ratio you have set to the CPU. Since the Athlon 3000+ XP has a FSB of 333 lets pretend you have RAM that is PC2700 which is also 333 in this scenario you would have a 1:1 ratio CPU:RAM see what I mean? Because both are sitting on a 333FSB....now when you RAISE your computer FSB from 166(333) to say 170 then your new FSB will then be 170(340) so then your RAM is running at (340) because unless you change it, the computer is running at a 1:1 ratio.
So a few things you need to look for in your systems BIOS are the options to Lock or simply select the desired speed for your AGP Bus which needs to be 66MHz...
You need to have an option for your Vcore, and Vdimm voltages (Vdimm just incase you decide to OC RAM later on down the road), and access to a CPU to RAM ratio option so if you don't want to OC your RAM you can select the RATIO that'll keep it at it's designed speed.
I'd say the reason your getting those blue screens is due to 3 things, lack of Vcore, RAM being OC'd, and possibly the AGP being OC'd, so check into all those things
Let me know if you need some more help