The easiest way is to pay $130/month to use the actual stack overflow. If you're not a web programmer, and you're using it for a company (internal, you said?), it would make sense to just pay for the hosted, supported service, wouldn't it? I mean, the cost would probably be significantly less than your value in man-hours constructing and hosting the thing.
http://www.stackexchange.com/
Of course, it'd be more fun to write it yourself. And your financial hands may be tied. Your company may be more than happy to let you spend months on a project, but won't be willing to spend cash from another, non-payroll bucket. In that case, be aware that what you want to write is a fairly simple application at its core. 99% of your effort will be refinement. Please see the other gentleman's answer referencing this blog post that you should certainly read: http://www.codinghorror.com/blog/archives/001284.html