To view the file without saving it, check Open it, then click OK. The application should open, allowing you to view the file.
If you saved the file, locate the folder where you saved it, find the file and double-click on it. The appropriate program should open. Alternately, you can first open the associated application--for instance, Word if the you received a ".doc" file--then locate the file and open it.
Click on Tools, Options, Security Tab, Select Allow Attachments
Sometimes you can not open attachments because you do not have the proper program to open it. Some possible programs you may need for opening attachments, are Adobe Acrobat Reader (in Downloads), WinZip (in Downloads), or one of the programs in Microsoft Office. Although you can't download Microsoft Office, you can download programs that will let you view files for most of the programs in Microsoft Office. Go to http://www.microsoft.com/office/downloads/default.asp and go to the bottom, you'll see a list of the programs contained in Microsoft Office. Just click on the program you'd like, then near the top, you'll see Search for downloads. The program you selected, will be in the box. You'll see 3 colored boxes, Red, blue, and yellow. Make sure the yellow one is the only one selected, then click update list. After the page loads, look for a listing down below that is listed as viewer, and download it.