If you haven't already tried it, I really do suggest you try repairing the Office installation (via Start > Windows Control Panel > Programs > Programs & Features > Microsoft Office (version) > Change>Repair). As I said, reinstalling Office rarely achieves anything a repair won't. Repairing might also resolve the crash issues.

I'd also recommend setting the autosave frequency for each app to a suitable minimum (I use a 1min frequency and find it has little impact on performance!). You might also try breaking large files (especially Word documents) into smaller ones (e.g. on a Chapter basis). Aside from the fact they'll perform better, you'll have less work at risk in the event of a crash. They can be recombined in various ways when you're done editing.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]