[davidhansen]

The product is probably about 90 % done already, the last 10 % should take no more than two weeks

Spoken like a true non-technical cofounder :)

Sorry to be the bearer of bad news, but the the pareto principle applies heavily to software development projects. It's quite likely that the "last 10%" will take much longer than you think.

That said, I've seen this happen quite often from inexperienced developers, and it sounds like you have one on your hands. It's easy for passion and ego to carry a project from a blank slate to a state of mostly-functioning. Hackers usually get a great rush from this stage of the project. It's their code, their architecture, their baby. Sure it's got some rough edges, but the important stuff is done. Their genius has been imbued into it, now comes the drudgery of polishing the edges - oh wait, this sucks. The process of turning something that works into something that's usable or salable is boring. What a letdown. They just solved this intractable problem in O(log n) time, and now you want them to make the interface's corners rounded or add some copy? Bah. They'd rather stare at the wall.

This is a total shot in the dark here, but I've seen it often enough that I'm fairly sure it's the mentality you're dealing with. And I can't say there's an easy solution. It's nearly impossible to motivate hackers who think creating software is all fun, all the time. You either chose a bad cofounder, or just a young one who needs some exposure to real software development projects. either way, I'd recommend a confrontation, followed up by hiring out if things don't change.

[jayzalowitz]

I have to agree with this.... Depending on how long he's been at it, it may be one of those "I need a second" my best suggestion is to get a deadline and show you are working your ass off as well. Basically, you need to do everything else you can and be there to get him pizza...

Consider bringing in a 3rd that you can give ~5% equity who can focus on problems he needs help with... ask for his help in this conversation...

[seiji]

"The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time." http://en.wikipedia.org/wiki/Ninety-ninety_rule

You could also go Pareto and say the last 20% takes 80% of your time, so take the time you've spent already and multiply it by 4 to get your remaining time until completion.