Zero-installation applications can be run from USB sticks and are extremely useful for troubleshooting.
Spread32 is shareware and can do almost everything Excel does. It does not support Visual Basic, but it can run Excel 4 macros. 912KB
Atlantis Nova can edit Word documents and save them as .RTF. 1MB
With an installation size of 275MB for Microsoft Office XP, and about 250MB for OpenOffice, the tiny 2Mb for Spread32 and Nova is a small price to pay for two very useful applications on your troubleshooting USB stick.