That's only one of several cases where I've recommended a truly good, open source or freeware app for Windows, to have the person become angry with me for sending them on a spyware-laden wild goose chase. From now on I just offer to install the app they need for them, using ninite.com instead of the original source. And it shouldn't have to be that way.
[1] http://forums.getpaint.net/index.php?/topic/23234-can-paintn...
Windows users do not constitute a "community". So if something's zero-financial-transaction-"free", it may still be bundled with exploitware and negative-added-value software.
But it's not for everyone. Most of my clients in the past have had specific commercial software requirements, so I wouldn't even bring up switching platforms. These days it's easier, as everything is moving to software as a service and web apps, and they are already used to running their home office from their iPad or Android tablets. Still, I make sure that my end goal is to offer the best value to my client, not push potentially unfamiliar and net-cost-ineffective solutions based on software license alone.