Please Advise

[adviceseeker]

I already have a stamped visa (H1B) from my old company (company A) which has a valid stamp until May 2007 . I got it stamped in May 2004 . I however , changed my employer this year , August 2005 to be precise . Do I need a fresh stamping for a new employer or just a letter (or whatever its called in technical language) should be enough for me to re-enter US (Right now I am in the US , but plan to go for stamping only if I need to)
Immigration Gurus Please help
Thanks for your time
Newbie

 

[GotPR?]

valid visa stamp with old employer and valid approval notice with new employer are enough to reenter.