Hi, Terri.
Step 1: Don't panic!
Quicken always makes automatic backups every week (unless you've changed the defaults). It stores these backups in a subfolder that it creates and names BACKUP (note the ALL CAPS name) under the same folder where your data files are stored. If your main data file is QDATA.qdf, and you haven't changed the default, you should find your working fileset in C:\Program Files\Quicken and all your 5 most recent weekly backup sets in C:\Program Files\Quicken\BACKUP. You may, if you like, change the default location, but If you didn't change it, that's where the files should be.
As Han said, a Quicken "file" is actually a set of related files, all with the same name and different extensions. We often refer to the entire set as a "fileset". You need them all, and Quicken handles them all as though they were a single file.
Now, how to find the files on your hard drive if you've lost track of where they might be? When all else fails, we can always use the current version of the old MS-DOS command, Dir - for Directory, now called Folder. At the Command Prompt, or in a Run box, enter: dir C:\*.qdf /s/a
Dir - the command to produce the directory listing C:\ - starts in the Root (the top level) of Drive C:
*.qdf - lists all files with the .qdf extension, no matter what name /s - searches all subdirectories under the starting directory; since we are starting in C:\, it will search ALL directories (folders) on C: /a - lists ALL folders and files, no matter what Attributes are set, so it will show Hidden files, too.
You may have time for a cup of coffee - or even lunch if you have a large drive with lots of files. But when it's done, you should see a list of EVERY *.qdf file on your Drive C:. If you have multiple drives, you can repeat the process: Dir D:\*.qdf /s/a, for example.
For every .qdf file shown, carefully note the complete path to the folder. Then browse to that folder and look for QDATA.* files. In your Quicken folder, or other location if you've changed the default, you should find a single set of all those files. In the same folder, you should find a subfolder named \BACKUP; in that subfolder should be FIVE sets of files with names like QDATA1.qdf, QDATA2.qdf, etc. In other words, they should have your data filename with a numeral added, plus the .qdf and other extensions. The sets should be dated one week apart. The QDATA1 set should be the most current, and dated no more than a week ago.
You may have other .qdf files scattered around your hard drive, depending on how many times you've saved backups or other copies. You may want to hold onto all of them until your recovery is complete enough that you can delete any clearly useless ones.
When you have located the latest - or the most likely current - set of files, just click on the QDATA.qdf file. Since you have already reinstalled Quicken, that click should start Quicken with that particular Quicken file loaded. When you are satisfied that this is the file you want to work with, click File | Backup and browse to the location of YOUR CHOICE for keeping the backup. (This is in addition to the automatic weekly backup, which Quicken will automatically put in the \BACKUP subfolder under the folder where that .qdf file is found.)
If this is not clear, please post back with questions.
RC