What Version of Microsoft office you have?
Open your excel again go to file and save as,
And name it and put this on the end of the name .xlsx
Example "Excel.xlsx" This is For Microsoft Office 2007
Hope it helps:)

Are you referring to Microsoft Access, the database program? If so, Access doesn't have documents, it has a file format. Depending on the version the files are named with the extension mdb or accdb.

Where are you seeing that its being saved as a Works document? My suspicion is that you have changed the association for mdb/accdb files to Works. If that's the case, you can right click on the file in Windows Explorer and select Open With. Then find Access and select it making sure you check off the Always Open With checkbox. That should fix it. If not, you need to explain further.