Shut Up, Laura

Q: "I have a DC that's been offline for about 3 months, how do I bring it back online?"

A: "In its current state, you don't, as you're beyond the default 60-day tombstone lifetime. Flatten, metadata cleanup, re-dcpromo."  (Funny, I seem to give that advice a lot when it comes to DCs.)

You'll notice that I've glossed over the "unless you created a pristine AD forest using 2003 SP1, but not 2003 RTM or 2003 R2, in which case your default TSL is 180 days" part, because the schema.ini regression in R2 can be a bit cumbersome to explain quickly.  Interesting to note that 2003 SP2, having re-re-re-disposed of the monster, puts the default TSL back to 180 days again: http://support.microsoft.com/kb/924890.