Cannot change registry settings back?

[geeoff1]

I changed the level 2 cache setting in the registry to make use of all 512k on my old early P-III 500mhz. I've just upgraded to an 800mhz coppermine. Whether I change it to 0 (256k) or 256, after the restart, its back to 512k. I've been told that if this setting is wrong like this, it will seriously slow down the machine. Anyone have any ideas? Thanx!!!