Hello.

Context:
H1B (I-797) expired in July '07. I-94 expired on Aug 4th 2007. H1B extension was filed (same employer, A), before the I-797 had expired. A few days back, I received the receipt number, yet to receive the approval notice (I-797)

Question:
[I read a lot of messages on this forum with similar/same situations. Still lack clarity and assurance. Any help will be appreciated.]

Given the context above, can I join a company B? If yes, how will they be able to file a H1B transfer if I do not have the approved I-797?

Thanks.
Nikki