Picasa3 is a desktop program that scans and indexes photos and video files that are already in folders on your computer's hard drive disk (i.e. "My Pictures") or your desktop, or anywhere else you place photos and videos. Any photos or videos you see "in" Picasa are the exact same photos and videos that are on your computer. Any other photo editing program on your computer can also see and access these photos and videos.
You control where Picasa looks for photos and videos on your computer by going to the menu Tools > Folder Manager and selecting folders to "scan always." Picasa displays those photos and videos to you. You can edit photos using Picasa and apply and save edits so that the edited photos can be used outside the Picasa program.
Picasa does NOT make its own copies of your photos!
When you install Picasa on your computer, it scans your computer's hard drive to find all applicable photo files. It then displays your photos to you. Picasa does not add, move, copy, delete, archive, back up, upload your photos to the Internet, or do anything else with your photos (other than locating them and remembering where they are) unless you specifically tell it to.
Picaca NEVER moves your stuff around automatically. When you install Picasa, it FINDS your photos. It leaves them right where they were on your computer, and it presents them to you for organization, editing, and sharing. It doesn't "convert" them into anything. They remain in the exact same folders on your disk that they've always been in.
Picasa shows you a "flat" view of the folders (by default) in its folder list. That's just a VIEW of the folders. Nothing on your disk has been changed.
You can view the more normal tree view of the folders by clicking View > Folder List > Tree View. Again, nothing is being moved around when you do this. The photos themselves always remain right where they were on your disk before you ever installed Picasa.
Since Picasa does not physically store your photos, if you delete a photo from a folder while using Picasa, the photo will be deleted from your computer.
Picasa is always working directly with the photos on your disk. Once the photo has been deleted from your computer, Picasa will no longer be able to show you the picture.
If you delete a photo from a folder using Picasa, it's exactly like deleting the photo from the folder using Windows Explorer.
Sometimes, people make a really bad assumption that Picasa has somehow created its own new copies of all the photos. So they delete everything they see in Picasa. What they're doing at that point is really deleting the real, original photos from their real folders on their disk. That's a HUGE mistake. Try a photo recovery program to get your photos back - some programs are listed here (the link will take you to another page. Please use your browser's back arrow to come back and continue reading where you left off).
Deleted photos end up in your computer's Recycle Bin. Picasa does not show you photos that are in the recycle bin. If you delete a photo by mistake, go to your recycle bin as soon as possible and restore the photo. Or go to a backup to get a copy of the deleted file. If you don't see the pictures in the recycle bin, refresh the window (right click an empty space > refresh; or View > Refresh). There could be a possibility that your recycle bin settings were NOT sending deletions there. To avoid this happening in the future, change your recycle bin settings. On your desktop, right click the Recycle Bin, then click Properties. Confirm that "Do not move files to Recycle Bin" is NOT checked.
Yet another reason why you may not see deleted files in the recycle bin is that you have a NAS (Network Attached Storage) system - these systems do not send deleted files to Windows recycle bin. Check your NAS drive's manual to see if they have a recycle bin.
You can use Picasa to delete folders and pictures off your computer disk. While in Picasa, you can click the delete key or click File > Delete from Disk. But use caution when deleting. Make sure your backup is up-to-date before deleting anything.
One thing to watch out for is deleting a folder while you're in the Flat View. Deleting a folder will ALWAYS delete that folder and any NESTED folders. If you're deleting folders, we suggest you switch to the Tree View of the folder list so you can see the ramifications of deleting a folder.
To avoid deleting by mistake in the future, make this change in your Picasa settings:
Click Tools > Options
Click the General tab
Under the "Files" section, do NOT place a check mark in the box that says "Delete from disk disk without confirmation"
Also leave the box blank for "Remove from album without confirmation"
Click OK
The best advice we can give to avoid loss of photos is to MAKE BACKUPS of all your files BEFORE deleting anything, and to make backups regularly - whenever you add new files to your computer.
When you uninstall Picasa, it removes the PROGRAM only. Uninstalling Picasa will NEVER, EVER delete any photos. You can install Picasa and let it discover your photos. You can then uninstall it. Not one photo will have been moved or deleted. Guaranteed. Be sure to save any edits you may have made in Picasa if you want to save the edited version of your photo. Uninstalling Picasa3 will not delete any photos you uploaded to Google Photos.