I don't know about you, but I seem to have old TSR adventures lying around everywhere, even after a house fire.  I have old monochrome cover copies of some things, and some stuff that people have never even heard of nowdays, like dungeon and city geo-morphs and the DM's helper (Gee, that's a product I wish they would reprint, the charts in it were soooo handy, along with the record pages).  Anyway, I've often been irritated by the fact that many players own some of these modules, and together, own most of them.  So that large bundle of someone elses creativity was doing my absolutely no good, not even counting the fact that the modules were not designed for Ravenloft.
  My younger brother and I were sitting in the front room one night, in Texas, while my wife was in Roswell, New Mexico on a field problem, thumbing through old B and X series modules, and laughing over the time that my Paladin, weaponless had kicked open a door to the goblin armory in B-2 and started hucking helmets at skeletons (wandering mosters), and laughing over the ever feared Dungeon of the Mad Hermit, a place where the room after you fought 14 trolls in a 30x30 room, you would run into an anklysarous (spelling???) in a 40x70 room.  No rhyme or reason, just lots of traps, monsters, loot, and bodies of dead PC's.
  "Can you imagine the Isle of Dread in Ravenloft?" my brother laughed, taking a sip off of his Jack and Coke, "I think it would have to be an Isle of Terror."
  "Ya think?" I replied sarcastically, then brightened, "Hey, it could be in the Sea of Sorrows, but the Darklord would have to be something cool."
  "How about a vampire?" James asked, nodding at Van Richten's Guide to Vampires.
  "Come on, another damn vamp?" I answered, somewhat sarcastically if I remember. "What about some kind of specter?"
  "What is your obsession with those things?" James asked, shaking his head, "Lhere Khan is bad enough, we don't need a ghostly Darklord.  We need something different, something fitting for the Ilse of Dread."
  "What about a T-Rex or raptor?" I asked.  James' face lit up, and we began installing a Raptor of high intellegence and great evil, who preyed on other dinosaurs, and believe it or not, primitive humans, more for fear and suffering than food.
  (No, I can't post the details.  By using the maps from some TSR products, I already run the risk of running afoul of thier legal department, I can't afford to post that one.)

  OK, enough strolling down memory lane, you get the gist of what happened.  Soon, I was converting everything from In Search of the Unknown to Lost Shrine of Tomachican for Ravenloft (By this time my group had pretty much deserted Forgotten Realms) and the players were being driven apeshit.  As unlikely as it may seem, even the Queen of the Demon Web Pits series (G1-G3, D1-D3, Q-1) was usable in Ravenloft.
  Here's the deal.  First open the module up, and look at the maps of buildings.  Ignore what they are supposed to.  I'll use the Slave Lords series A-1 through A-4 (I don't have the combined one anymore, so Oh well)
  Let's see, we have, a ruined temple, a stockade, two underground labyrinths, a semi-recovered stockade, and first a small city, then a hammered city.  Hmmm, useable.  Let's put it on the edge of Falkonovia, since that country has gone to was with Darkon several times, and there is bound to be some lingering damage from the wars.  Let's put A-3 & A-4 in that lake by the Darkon border, the chapel and stockade up by the border.
  Big question here, do we keep the Slave Lords.  Could they survive.  Yes, providing they payed the correct tribute to the correct people.  The old Slave Lords will have to go, since it was set up for Oearth (Greyhawk).  We need new villans and new creatures inside the modules, since the old ones do not have the correct flavor.  Do we want to keep the modules together, with Slave Lords, or do we want to reconstruct them.  Keeping it with Slave Lords won't be that hard, so I guess we'll focus on the reconstruction of the modules.
  OK, we have some nice facilities, and a location, what shall we set it up around?  Let's see, a magic item, a criminal, a group of monsters, or a major villian?  Let's go with all of the above, since that is pretty easy.
  How to get the PC's involved?  Hmmm, we can have them wander into it, or hunt them down purposefully.  A little tougher, and something I can only help with a little bit, since I don't know your players or DM'ing styles.
  We need a plot.  Hmmm, let's see, a good plot that would use all of those areas.  Ah-ha!  The most coveted thing in a Ravenloft campaign.  No, not a 30th level Cleric, but a Rod of Ressurection, usable only by Good Aligned characters!  The search for a Rod of Ressurection is a valuable one for the party.  The logical place to start will be the temple.  The quest for the Rod will take them into contact with our villians, and will be a nice campaign addition.  Why do the PC's want the Rod of Ressurection....hmmm.  Sometimes PC's don't want or need one, but what if they need to raise someone from the dead who is important.  What about an NPC who could provide important information?
Next problem:  Filling the place up with creatures and people, and giving them a Ravenloft flavor.  All right, the 1/2 Orcs in here will be very strange to people who only played second editiion.  Not to many people will have really noticed the 1/2 Orc in the Skills & Powers book, or saw it and thought nothing of it.