GETTING 64 MBs when installing 128

In an IBM 200 MHZ Computer (Pentium), a client had only one 32 MBs in one slot.
The Manual says we can install 256 MB in the two slots.
We gave all the info. to a Computer Memory seller and purchased 128 MBs.
Unfortunately, the maximum memory we got, was 64 MBs (“164 Memory Configuration error”)and the minimum 32 MB, using all possible combinations.
In other computers, the 128 MBs gave the correct memory installed.
What should we do in order to get at least 128 MB or using both slots 160?

MrWayToGo@aol.com