.lnk is a link used in a shortcut (the link between a shortcut and the program associated with it). To change the download.lnk back to it's original state you can right click on the Downloads icon and under target change the target to: C:\Users\UserName\Downloads. You will substitute your user name for "UserName". This will only fix the association for downloads. You could also try to right click on the other shortcuts and click on Open with... and change the shortcut associations by linking them to the appropriate files/programs. This may take a while depending on the number of shortcuts you have. Another option is to restore the system to a date before you changed the .lnk association. If you are unable to do that then the best choice might be to have the school's computer techie and have him/her fix the problem.