Hi,I am having the same problem on 3 new HP Compaq 6735b. None will boot up Windows 7 RC whilst on battery power. all frezze at the boot screen. plugging in to mains power (even once the laptop has frozen) boots up the computer fine. all enter and exit from sleep fine on battery power. No problems on XP or Vista. any help would be appreciated. thanks,

Hi,it's looks like some drivers are not properly works when you on battery power. Try to update your BIOS or change power management options into BIOS, uodate your chipset driver. Have you ever tried to boot your laptop in the Safe mode (pressing F8 button befere W7 logo by default)? If the same problem in the Safe mode - contact with your hardwaresupport (HP) and try to consult with them. IMO it's your HP hardware (I mean hardware drivers) problem, not a W7 problem.Hope it helps. My English is not very well.

I had the same issue with my 6735b.There is a BIOS update from June 24th of this year that I had to upgrade to in order to get it running. Without the update it wouldn't boot up on battery power alone. Now interestingly I was able to get it to boot up on battery if a NIC card was plugged in, but.It also seems that they just uploaded a new BIOS from July 31st, but you should be fine if you just do the June 24th.