Hello gillianpollock,
The simple answer is No you can't undelete a file that was deleted 3 years ago. The file has been over-written so many times by your computer within the last 3 years that there is probably not a trace of the file left.
When you delete a file it doesn't actually delete it, it simply marks the area as available. As you use your PC the 'free' space, i.e., the space taken up by your deleted file, is filled again with date. This over-writes whatever was originally there.
You have a better chance of recovering a deleted file if you attempt to do so within minutes of you deleting it. The longer you leave it before recovery is attempted the less likelihood of you ever getting the file back.
This forum post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.
John Barnett MVP: Windows XP Associate Expert: Windows Expert - Consumer: www.winuser.co.uk | vistasupport.mvps.org | xphelpandsupport.mvps.org | www.silversurfer-guide.com