you can even use the windows inbuilt calculator.....
from view, select scientific.....press F6(to ensure that u r entering the numerals in decimals)....then press F8...the number which is displayed is the binary form of the nunmber which you entered earlier.....u can use this in vb6 then
eg, i pressed F6....entered 4784and then i pressed F8....the number which was displayed was 1001010110000 which is the binary form of 4784
p.s if you don't wanna press F8 and F6, there are radio buttons on the left(top) corner of the scientific calc....use that