column 7, row3 has to be a 3. I came to this conclusion because a 3 is already in column 9, and it must be in row 3 because there is nowhere else the 3 can go for that row. That leaves us with columns 7 and 8 to possibly hold a 3. Rows 4 and 5 in column 7 must contain a 5 or 9, since they can not go in any other square. That leaves us with the one 3. Ta da! I hope this was understandable >>.
This puzzle is actually only a 3 star. I feel pretty worthless for not getting it >_>;; But it is pretty tough.
Edit: Actually Cless, Ackbar is correct. The two squares below row 3 col 7 must contain 5 or 9, and since there must be a 3 in Col 7, and no other row in that column can hold it because of the 3 in row 8 col 9, it must be row 3.
Edit #2: Having said that, the new 3 doesn’t help me deduce anything else at all >_>;;;;
Edit #3: My mistake, it DOES. That 3 was very useful