CPU Vcore and DDR Vcc - What Are They?

I have an ECS L7S7A2 mb with an AMD 2400+ and two rows of 256 DIMM SDRAM. The default CUP frequency is set at 133. Whenever I bump it up things get wonky. XP will start, but it wants to fix dicrectory structures at startup, it crashes randomly, and it porks some .exe's. I have two fans in the case - one drawing air in and the other pushing it out. Things don't get hot so I do not think it is a heat issue.

The only setting I really toyed with was the CPU frequency. So, do i need to tinker with the Over CPU Vcore Function and/or the Over DDR Function? Also, what do they do? I have no idea what they are for. The settings possible for each are CPU Vcore: NOrmal, +5, +3, and +1. The DDR Vcc function presents the following options: Normal, +3.5, +2.7, and +0.8.

Anyone in the know here? Also, will it be worth upgrading the BIOS? I know that is always recommended, but I think it is just because it is, if you know what I mean.

Thanks for any input.