How to stop lightroom catalogue syncing with your onedrive?

Boy, reading some long explanations on why you should use onedrive and how it functions was exusting.  It is a simple question and I have the same problem.  I reinstalled windows and onedrive took over my lightroom file which screwed up my catalog and I haven't been able to recover my catalog because onedrive is holding it hostage.  

Simple. TAKE THE CATLOG FILE OUT OF THE ONE DRIVE FOLDER.

It should not be in there in the first place.

Never place your catalog in any folder on your computer that syncs up with a Cloud Storage system.

All you will end up with is a Corrupted catalog file.

You have control over two aspects of LrC working: where your Catalog and its support files live (previews, chiefly) - and, where your imported image files live (camera Raws / JPGs, derived files such as PS edited versions saved in PSD / TIF) live.

You also have, separately, control over where output files are to be saved.

If any of these locations are withiin a part of your file system that is being synced to OneDrive, then any change will then incur some OneDrive activity - which may or may not be useful or appropriate. IMO the most likely, is that you have accepted for OneDrive to keep your personal drives backed up to cloud. And that will include your Pictures folder. I did this recently, incautiously, and the file system locations of my Documents, Pictures and Desktop were changed to sit within a "OneDrive" folder representing the local instance of the OneDrive synced data.

LrC's install default is to create a Catalog within Pictures, and then to offer to import all image files within Pictures and subfolders thereof. IMO this is an inappropriate place for certainly the Catalog to live, even more so once that is syncing to OneDrive. It is at best impossible, and at worst inadvisable, to back up the Catalog itself while in use - the database and its indexes may not be in a clean and consistent state at that instant. All kinds of previews live in subfolders of the Catalog location, constantly changing, and it is IMO a pure needless waste of effort to keep backing those up continually. It's really the Catalog itself which matters, besides the source image files. Previews could always be generated again if that was ever needed. One idea may be to locate your Catalog elsewhere, outside the OneDrive synced area, but then to set a folder within this area as the destination for your LrC catalog backups (made cleanly, as you determine, on exiting LrC hence known to be suitable for restoring). Dated backups will then accumulate and will need periodic pruning. But you will have some history available, to roll back through multiple versions. Sometimes a problem arose last week, and everything backed up / synced since that moment, includes this problem - so we are not then seeking the most up-to-date version to restore.

Imported image files are not continually changing as you work on those nondestructively, unless you are automatically writing edit changes out to XMP. If using proprietary Raw this will manifest as small sidecar files that OneDrive would then be constantly syncing. If using camera JPG or if converting to DNG, then the entire big file would be constantly syncing with each edit change. And externally edited (such as Photoshop) files would be re-syncing with each save to those. IMO it may prove unwieldy to have all this stuff continually synced; better to have some other backup method carried out on demand. One important aspect there IMO, is that deletions should NOT be synced out. One purpose of a backup is to still have a copy of that file, which you have locally deleted or overwritten in error. In that case you won't want that backup to have, faithfully and promptly, mirrored that same deletion or overwrite.

However IMO, the Pictures folder is a completely appropriate place for exports to be saved into, and it makes perfect sense for these to then go out to OneDrive automatically. 

Changing the location of the Catalog itself is straightforward and does not require any re-addressing of the image file paths that it references. Changing the location of the image files will require updating those file paths within the Catalog (regardless of whether the Catalog has moved or not). That's re-addressing, not re-importing BTW!