azayzel54

Actually there is a plugin folder. If you use SKSE- the location is (at least mine is) Steam > steamapps > common > skyrim > data > SKSE > Plugins

I don't have the Book of UUNP Iron and Steel and I just encountered the same crash message. Mine happened while on the quest The Wolf Queen Awakened (potema's second quest; talk to Styrr, etc. etc.). I CTD'd 3 times while going through the catacombs; the last time was in the room with the spinning light and room full of undead. I don't believe it's the Book of UUNP because I don't have that installed, and there is a bug associated with the Wolf Queen Awakened: http://www.uesp.net/wiki/Skyrim_talk:The_Wolf_Queen_Awakened (crash to desktop bug) (for those that have it happen during this quest line). Something to do with clothing (which I don't have in my mesh clothing folder) on Potema.

The main issue with Dawnguard (I know I'm responding to an old post, but..) is that it needs to be cleaned with TES5Edit twice. If you look up on how to clean a mod (using LOOT will reveal the dirty issues a mod might have, or in the case of Dawnguard after you clean it once it won't say that it's still dirty) you have to clean Dawnguard twice. It's one of the more buggy DLC's. Also, I suggest getting the Unofficial Skyrim Legendary Edition Patch if you have all 3 DLC's. If you have all 3 DLC's, getting the patch for each one isn't a good idea. And definitely consult notes or any additional information like Better Vampires has on its mod page. A lot of troubleshooting posted recommended instructions for problems such as the one you're having