@Pavel, you cant use old nikon flashes with digital nikons due to lover triggering voltage in digital camera. You can still use them in manual mode if you put safe hot shoe between camera and flash.
Im positive all brands have same "problem", including pentax.
Nikon TTL flashes that appeared together with FG are low-voltage, that's not the issue. TTL flash with rotating head will satisfy 99% of what an amateur needs, all this "computerized control", "digital interface" etc are just marketing slogans. The problem is that film cameras with Nikon hot-shoe, like F65 or F80 work exellent with plain TTL flashes introduced in 1981, while DSLRs simply refuse to recongnize any flash except maybe SB-800 and later. Why should I pay hundreeds of dollars for the same result that I can achieve with a $30 piece of plastic and wire made in China?
Hmmm... Just understood that I tried my Vivitar TTL flash only on D70, there is a chance that it may work on D200.