An attachment to an email in a web based client like Gmail or Hotmail in Internet Explorer may be recovered even if the user has not saved it. Gmail will attempt to open a lot of standard Office files in Google Docs, and Hotmail will give you the option to view attachments in the online versions of Word and Excel. However if you don't use these options and download the file, IE should save it in a folder for temporary files, which in Windows 7 ought to be located at, C:\Users\[your user name]\AppData\Local\Microsoft\Windows\Temporary Internet Files . You can find the location for sure by going Tools . . . Internet Options . . . clicking on Settings in the Browsing history section, and then looking for 'current location' on the Temporary Internet Files tab. The files may be retained for up to 20 days, or longer if a change has been made to the default setting for 'days to keep pages in history' on the History tab on the same Settings window. The downloaded file should be renamed with a very long file name containing a seemingly random series of letters and numbers. If you have trouble opening it and get an error message in the IE browser referring to a 'bad request', try copying the file to a regular folder on your hard drive. The file should be renamed with its original name.
The Chrome browser stores temporary internet files at: C:\Users\[your user name]\AppData\Local\Google\Chrome\User Data\Default\Cache but will put downloaded files in a download folder in a location such as, 'C:\Users\[your user name]\Downloads'.