What computer operating system is your Premiere Elements (presumed 12) running on?
Where is your export being saved to....external hard drive fomatted FAT32 instead of NTFS?
Let us back up...
a. What is your project preset (see Edit Menu/Project Settings/General and readings for Editing Mode, Timebase, Frame Size, Pixel Aspect Ratio even if the fields look grayed out).
b. What are the properties of your source media. Any Cineform.avi in the mix?
c. Does your project preset match the properties of your source media?
d. When you get to Publish+Share/Computer/ what do you select next? And, then what do you select for Presets? Are you customizing the preset under the Advanced Button/Video Tab? If so, how? Just before you hit the Save button in the export area, what do you see for the estimated file size and duration?
e. What is a description of your computer resources?
Let us start here and then decide what next.