H4 to H1B VISA

[virtual55]

I am having my H4 visa till 2006 and I got my new H1 papers and I want to go for H1B visa stamping before start working on my H1B. what happens if they reject my H1B visa. Will they cancel my existing H4 visa also?

 

[max2k1]

I am having my H4 visa till 2006 and I got my new H1 papers and I want to go for H1B visa stamping before start working on my H1B. what happens if they reject my H1B visa. Will they cancel my existing H4 visa also?

I don't think you need to necessarily stamp the visa before you start work.
The approval papers should be sufficient.

AFAIK, when you get a H1, your H4 status (hence the validity of the visa) is gone ... am not 100% sure of this but very close to that -- check with an attorney.
To get back H4, I think you need to make a trip out of the country and come back.