Sirsha.com

Well it's not fair for *you* to do it for *free*. Hmmm. I wonder if any trial lawyers are listening. Sounds like a *massive* class action suit to me. :)

Mike, your URL is messed up in your comments you've left...

Argument #1: The client is the one who decided to low-bid you into taking shortcuts with the code that resulted in future incompatibilities, and they alone decide which service pack they want to run.

Argument #2: You are the one who designed the software to do something nasty that raised the ire of a more security-conscious operating system, so you should share the burden of secure code with Microsoft.

Personal preference: I think it's a mix. You should offer to fix the issue for time and materials, and then not charge 100% of the time since you are the guy who wrote the bad code in the first place (*never* drop your rate, even for a single hour).

Of course, all this assumes that the *reason* for incompatibility is the new security features in XP. If it is because of other unforeseeable changes to the OS, the client should either pony up the cash to migrate the application, choose to not upgrade, or stop using the app.