[Adoby]

I didn't say anything about upgrading. I assumed that you are using the latest version of calibre. If not, just upgrade. Nothing special.

And delete columns you don't use. Especially the formats column if it isn't based on approximate formats.

And check for columns that are not displayed. Delete them if you don't use them. I remember cases when users insisted that they didn't have any formats column, that checked the files on disk, but it turned out there was one after all...

If you want to see if a fresh library will improve performance, create a new library and copy the contents of the old library to the new. You can do this from within the calibre GUI.

Also, if you use an old install of XP that is beginning to get shaky and slow, you might consider reinstalling the OS or upgrading.