Why does my Mac keep telling me that there is not enough memory when I need to open Excel?

Question

I have Excel installed on my iMac.
I only use this rarely, mostly when I have grants to write for my students.
When I try to open Excel, to look at an old document, I get the message that there is not enough memory, even though my Mac right now has 74 GB available.
I really, really, really need to access these files, so am hoping for an answer to this puzzle!
Thanks so much!!!

Answer 1

OK, so here's what I did.
First time, I reinstalled Office: 2008.  It must have sent the first one to the trash, because there were 9200+files in the trash once it was finished.  It looked for updates but didn't tell me that it needed any, so I tried to access Excel again, but got the same error message.
So, then I dragged the whole Microsoft Office 2008 to the trash (it is still sitting there----question about this, too).  I reinstalled the whole thing again, but this time, it identified 3 updates that also needed to be installed.  I did that, and now, I am able to open Excel!
Now my question about the trash:  if I empty the trash, am I going to lose all the files (especially worried about all the Word documents) that I had used the original one for, or, are all those documents, and the Excel files, still  there after the trash with the original Office 2008 is emptied; I wasn't able to only drag Excel to the trash so had to drag the whole thing.
Am thinking that somehow those updates were never applied, which is very puzzling, because the first time I reinstalled, it didn't say anything about needing updates, but the second time, it did.
Thank you!