Would need to know the rest of the system to suggest something.
In the first count no. The 4/8 pin +12v connector isn't interchangable with any other connector, graphics cards connectors can't be used instead.
Exception is when you are referring to a 4 pin molex that IDE/PATA hard drives, CD/DVD drives and AGP graphics cards use, if you have a motherboard that uses an aux 4 pin molex then yes, they are interchangable.
But as I said above, the 4 pin P4 +12v / 8 pin EPS12v connectors can't be switched with any other connector the PSU has and doing so might damage the board.