Can’t run defrag

When trying to run defrag (Start\Programs\Accessories\System Tools or from the c:\Windows folder)I am getting an error message saying there is not enough free memory to run the program. It suggests closing other programs and trying again. I closedeverything running exept Explorer and get the same message. The computer has 128MB of memory which it is seeing upon bootup. Could one of the memory cards be bad and not working properly even though it’s being detected? Shouldn’t defrag run with only 64MB ram even if one card is bad? How do I rearrange the memory to make more free? Thanks.