Like most of the other comments, I generally use printf / MessageBox statements for most things. But since I work on consumer desktop software, occasionally a

Like most of the other comments, I generally use printf / MessageBox statements for most things. But since I work on consumer desktop software, occasionally a customer will encounter a problem that I can't replicate on my dev machine, and their bug description doesn't help me locate the problem. In that case, I try to duplicate the customer's system as much as possible: I have Parallels Desktop & VM images of almost every version of Windows, and I can configure the amount of RAM. Sometimes it's easier to ask the customer to run a special Debug build, but if they're not very tech savvy, Parallels can often help me reproduce the bug myself.