It could be as simple as opening the Dell All-In-One Center, click on scanning and copying and update the list of applications to send scans to. I scan my documents to Open Office, when scanning text. Scanning to email produces a jpeg. Since you're not quite sure, try a clean install using the instructions I provided.

 

Disconnect your printer. Download and run this patch. It will remove the printer completely from your computer. Restart your computer.

 

 

Now go to drivers and downloads/select product/printers/select your printer. Download drivers.

Install your printer drivers. You'll be prompted when to connect it.

Scanning

Scanning using USB connection, open the Dell All-In-One Center, click on scanning and copying and scan from there.

Scanning wirelessly, use the scan buttons on the printer.

 

 

You could have accidentally changed the program that opens the documents you use. Find another document and make sure the right program opens the document for you. If it doesn'e then right click on the document, left click on open with, choose the proper program from the list, choose program and check the box, alway use the selected program to open this type of file. Noe every time you have that type of document, that program will open it.