Excel Not Enough Memory

I received excel files as attachments via email and when I try to open in excel I get “Not enough memory” error. These are files I receive on a regular basis and can usually open without any problem. Memory should not really be a problem. I just recently had memory installed in my computer. But it shouldn’t have been a problem regardless. I have tried saving the files to hard drive and opening but still get message. Files are between 30-32kb.
But I have noticed my excel responding very slowly. Like when I do a copy and paste. It takes a while for it to paste.