[X-Newbies] Out of memory message in OS X of all the darndest things!

[J]

I have to admit I have not updated my Powerbook G4 circa 2004 to a  
spiffy new Intel model only because I love using AppleWorks for  
simple lists and letters etc.

I hate, repeat hate, using Office for anything and have it just for  
compatibility. AppleWork's spreadsheet component opens MUCH faster  
than EXCEL and is usually all I need to keep text records of emails  
in case in an emergency I have to send out BCC, etc..

Recently while taking emails from an EXCEL file to put into a  
database for a mailing list online, EXCEL puts up this Out Of Memory  
Message. There are about 500 listings in it, so it's not THAT big. I  
only  had Mail and the webpage with the list software open while that  
was open.

This confounds me because I have never seen that on OS X and know  
that you cannot 'allocate' memory to programs like you could in the  
old Mac OS.

What's worse is, you cannot dismiss the message and must force quit.

I have not yet looked to see what info I might have lost.

How do I make this stop?
My computer has overall 1.5 G memory, is that not enough to run EXCEL?
MS Office is so danged bloated!