Screen becomes garbled

[Bancroft]

I have a population model in Excel 2007 with 600 rows and 1748 columns. After I have had it open for 30-60 minutes it will quite likely start to lose elements of the screen. Usually the right side of the menu bar will disappear first, leaving shaded boxes with no text. The same thing will happen to graphs on the screen. Even the X to close the file disappears. I try to close the program using File Exit before the screen is totally unusable. It took 40 seconds for Excel to count the cells with text in them in one row of my spreadsheet when I was trying to figure out how many columns I have. I am using a Dell Inspiron 9300 with a 1.73Ghz Intel Pentium processor and 2 Gb of RAM with Windows XP Service Pack 3 Version 2002. Excel will also cause my computer to use 100% of CPU, slowing or stopping everything.

Is this an Excel problem or is my computer too weak to handle it?

Would an Apple Macintosh handle this kind of number crunching better than a PC?

Thanks for any guidance,
Bancroft