Depending on the complexity of the OP's workbooks and the speed of his/her
Internet connection, OP could try using the free OpenOffice,
http://www.openoffice.org
There are several other freeware and shareware spreadsheet programs that
can
work with .XLS files, though few handle array formulas or external
references. Gnumeric 1.4 does, but it's in beta on Windows.