Excel 2007 : Rearranging data

i have data in the below format in column a
1
2
3
4

5
6
7
8

9
10
11
12

and i would like to have it in this format (in columns a b c...)

1 5 9
2 6 10
3 7 11
4 8 12

Please help its urgent

Thanks
Gunner