Workcentre pe 120i memory full

In spec. say's so:
your workcentre Pe120 have only 32 Mb memory.
fax function is equipped with a 4 Mb standard memory.
In spec. shows a 4mb memory is just enough for 320 pages of fax!!!

i think your problem is given from the 32 mb of memory of workcentre pe120, not from fax memory, because the faxes received or delayed is compressed with a very strong altgorithm, and these files is very small.

http://www.office.xerox.com/multifunction-printer/multifunction-under-30ppm/workcentre-pe120-pe120i/spec-enus.html#Memory

a link bellow ; i think is useful:
http://www.xeroxdirect.com/direct/public/products/accessorizer/dsp_accessory.cfm
for a 32 MB memory module (product code is: 097n01434)