Russell Beattie demonstrates how hard it is for a company to shed a bad reputation - he's very, very wary of Microsoft, even when they are doing generally good things:

Microsoft Bribery- Microsoft is using it’s $60 billion cash reserves to buy out everyone who it has stomped over in the past decade. Sun, Netscape (AOL), Novell and now Real. Do they really think that cleans up their image? The value they get from their illegal monopolistic practices far outweighs the pitances they’re paying out in renumerations. This round of settlements is just clearing up loose ends so they can start another round of aggressive business tactics (look at Sendo for a recent example). They’re also doing things like “embracing” open standards like RSS, opening up their Office doc XML stuff, licensing their mobile OS to Palm, and doing IM interop? Sorry, it all looks good, but is mostly an effort on MS’ part to improve its public image, no less. As soon as they can crush their current competition, they’ll be back to their same old ways.

Now, the general buying public doesn't share the nasty image of MS that a lot of tech folks do, which is why the generally bad reputation they built up didn't do more harm. Still, Russ' post shows how persistent that "first impression" can be. With many people, you may never get a chance to create a better one.