R help - Jan 2011 - Error using write.xlsx message <20110128124648.284440@gmx.net>

Here are the specifications from Excel 2010. There are others for older 
versions of Excel so you may need to do a search specific to your 
application.

http://office.microsoft.com/en-us/excel-help/excel-specifications-and-limits-HP010342495.aspx?CTT=5&origin=HP005199291

You should be OK looking at these specs.

However, in my experience Excel is a resource hog and this doesn't rule 
out a bug in Excel or Windows 7. Make sure you have all the latest 
service packs and updates loaded on your machine for Excel *and* Windows 
7. Windows 7 is still a bit new and may be still a little unstable.

HTH