Most people will rarely use WordPad these days, but it's installed on pretty much every Windows system out there. So when Microsoft announce a vulnerability in WordPad, it could spell trouble.. essentially, a specially-crafted WordPad file could run arbitrary code on your system.
WordPad documents have a .DOC or .WRI extension, and if you have Word installed (or a similar product) then .DOC files will default to loading in Word instead. So, to mitigate against this you could simply block .WRI files at your proxy and/or mail filter. Or you could use Windows XP SP3 or Vista.. but that's not exactly a quick fix. Or you could deassociate .WRI files from WordPad using a policy.
There aren't a lot of WRI files to test with on the web, so here's a harmless file I prepared earlier: