Our computer went down. This is where my iTunes account was set up with apps, books, and videos purchased. How do I get all these transferred to a new computer?

What type of computer? What operating system? If it is a mac just remove the drive place it in an enclosure and run Migration assistant on your new Mac. If it is a PC you can put the drive in an enclosure and transfer the contents of your user folder. If the hard drive is bad you will have to transfer from your backup. EVERYONE YOU GOT TO BACK UP

HP

Do you have a backup? Can you access the old HD you may have to use an external drive enclosure?
Applications bought through itunes can be redownloaded music can not however if you call apple they may let you redownload music you bought on a one time basis,