I have a HP Omnibook 6000 specs:

Pentium III 650mhz on a 440BX intel chipset
128MB ram
10GB hard drive

I have 2 slots dimm which is occupied by two 64MB ram pc-100 and i might getting a 128MB ram pc-133 and i'm thinking of pulling out one of my 64MB and putting in this new 128MB that i'll be getting tomorrow...and here's my question, would my remaing 64 pc-100 be ok with a pc-133 128MB ram working together? or would there be compatiability issues?

any input on this would be greatly apprecitated

They should work together, provided they are the same type i.e. both Non-ECC or both EC. Their speed will only be pc-100, even with the one 128MB piece in it, as your MoBo is too old for 133 (I think).

Make sure that all the RAM modules are of the same BRAND. Laptop can be picky when it comes to memory A PC133 will most probably work even though if your mobo doesn support it but at PC100 speed..

thanks! i held off on the ram for now because of this concern as i am doing a lil more reserch about this issue

PC133 will work fine in a board that only supports PC100, no problem there, and using PC133 and PC100 should give no problem either. My concern is if you are mixing brands. Using two or more different brands of RAM is a bad idea, as it quite often causes problems.