MS Word and MS Excel Vulnerabilities

I have the full MS Office 2000 Premium suite.

Since I don't need any apps other than Word and Excel, I've uninstalled all elements except Word and Excel.

To reduce size of C:\System partition (for System partition image backup), I've installed these apps on a separate D:\Apps partition.

Both of these applications have known security issues - but because of the way I've installed them, the MS Security Patches won't install.

I've never had a serious virus attack using NAV or NOD32, nor with current Trend IS2005 firewall+AV combo installed.

Questions:
1. How serious are these Word and Excel vulnerabilities?
2. What's the best solution to this dilemma?

Thanks for your help!