I have an external USB drive plugged in, but Picasa is not displaying that drive in "Folder Manager", and as such I'm unable to scan and view the photos on that drive.
Is there anything I can do to force Picasa to see my drive?
There are certain types of drives that Picasa refuses to list in its "Folder Manager" – generally these are drives formatted with the exFAT file-system, commonly used on USB sticks.
There are two possible workarounds to handle the issue:
If you locate and access:
You'll notice it looks like this:
D:\Photos\ D:\My Documents\ C:\Users\Simon\Desktop\ D:\Videos\
You can manually enter the paths to the folders that you want automatically scanned within Picasa.
Unfortunately if you later remove a folder from this file, it may not remove it from Picasa - it may only stop Picasa from repeatedly scanning it. For more control, you might like to use option #2.
The workaround for this is to map the external drive to a folder on another valid drive, such as one using the NTFS file-system. To do this:
Just be aware that if you later launch Picasa and your external drive is not plugged in, Picasa may think that the files have been removed and begin to wipe all memory of those photos (including thumbnails and other saved data). This is only the case when Picasa can no longer find the relevant folder, NOT when Picasa simply cannot find the entire drive. For this reason, you may prefer option #1.
There is a quirk where Picasa refuses to access drives A: and B:. If you happen to have your external drive mapped there, it's best to open Disk Management and assign it a different drive letter, or follow the workarounds above which should also work.