Are these the correct specs for your computer - http/panam.acer.com/acerpanam/notebook/0000/Acer/Aspire9810/Aspire9810sp2.shtml ? How much RAM do you have installed on the computer?
It seems as though the processor will handle a 64 bit OS. Remember that you will have to find the 64 bit system drivers if you decide to go from the 32 bit to 64 bit version. Do you already have a copy of the 64 bit version of Windows Vista?