This is not supported.
Photos transferred from your computer are optimized for viewing on your iPhone as part of the iTunes sync/transfer process - the original resolution of these photos is reduced. Photos on your computer should be included with your computer's backup along with all other important data.
There are some 3rd party paid utilities that provide for transferring these photos in the opposite direction, but the original resolution of these photos will be lost, and such utilities are not supported by Apple.
Here is one.
You can transfer photos from the Camera Roll to your computer, but you will have to recover the photos in the Album app from the backup of your computer that you made before it died. The iPhone is not a backup device.
See:http://support.apple.com/kb/HT4083 for informaton about the camera roll.
There are 3rd party apps that can get photos from the Album app to your computer but these are not endorsed by Apple. I mention PhoneView for Mac or TouchCopy for Windows. I have used neither and this is not an endorsement of either, just a statement that they exist. Note, however, that photos in the iPhone album app are "optimized" for the iPhone, which means that if they were taken with a higher resolution camera than the iPhone's they will be lower quality than the originals.