msi k7t266 pro 2 memory problem

have a msi k7t266 pro 2 mainboard with 1600mhz athlon processor.
running win98se
have a 256mb ddr pc2100 (266mhz) memory chip, recently tried adding another
256mb 333mhz chip, which resulted in startup problems and windows failing to
load,
messages included ...
problems with vtd, ntkern, initialising device ios, ndis, vcache, etc
most times couldn't get as far as safe mode, even when could and used norton
utillites to test memory , nortons reported memory problems,
bios registers the ram and have tried changing sdram settings in the bios
setup, with no luck,
when using the 333mhz chip alone windows becomes unstable, back to using
original pc2100 chip and it now registers 262mb in memory count at
startup....
anybody any ideas?
is this a compatibility problem between the different speed chips?
msi have yet to reply and list no bios updates, or mention of any problems
mixing chips , on their website.

 

Mismatched pairs of memory modules do not work well or at all with this
board.

Try running with "Load BIOS Setup Defaults" in the "Advanced Chipset
Features" in the BIOS Setup Menu. Your current memory timings appear to be
too aggressive for the 333MHz memory stick but are just fine for the 266MHz
stick.