There are pitfalls with Dell drivers if you get things wrong. Did you read click here and perhaps print it off for reference?
Do you remember what the icon that was attached to the downloaded drivers was like? If so you may be able to get back to it by using the "open with" option you used before. The other option would be to download the drivers again.
I suggest you read the information on driver installation in the link and see if that helps. If you then need more information post again.