HALP

char temp4[3];
unsigned long int FileStart;
FileStart = (temp4[3] << 24) | (temp4[2] << 16) | (temp4[1] << 8) | (temp4[0]);

This was supposed to take four bytes and turn them into a long int. How do I do this so that the << doesn't turn every byte other than the first one into 'FF'?

>>8 is right, and you can access the elements background like in Python:
a[-1] is the last element, a[-2]•••