udma 66 mode

i am running tweak xp, under the hardware tab there is an option to enable UDMA 66 mode for intel chipsets that support it, it is off by default. i cannot find anywhere on my machine(device mgr. ect.) in help and support nor on intels sight if my chipset supports this or not, as a matter of fact, i cant even find out what UDMA 66 is. i guess i could leave well enough alone, but im kind of a tweak freak and the thought of not tweaking something that i could is driving me nuts.

i run

winxp home
pent 4 1.8ghz
512 meg ram
80 gig 7200 rpm harddrive
the chipset is intel 845

You didn't look very hard. I did a Google search on "UDMA 66" and got over 74,000 hits.

thanks for the help, google answered half of my question, if my chipset supports it, i still dont know.