NO OS stated, are we to guess OS , windows what.
XP ,vista or 7
32bit and 64bit for 6 OS delivered while produced.
or W10 with the Free W10 upgrade, must I guess more?
what did it have new. XP? 32bit (x86)
then what do you have now, see? we cant guess what upgrades means. or updated. (windows update?)
compaq can be super old or up to 2013
lets see what your is.
camera the one built in to the screen top bezel that cam?
or added cam? or some USB camera> ?
here is your support page at HP real. we are not HP here.
https://support.hp.com/us-en/product/hp-compaq-6735b-notebook-pc/3687779/manuals
HP drivers are smart, they flat refuse to load on wrong pc
wrong OS or wrong camera. or PC is 64bit and you ran 32 drivers, by DESIGN.
see? my guess wrong all that. 1 or more....
see that?
if hp camera (built in)
click os here. and bits (above link has all that)
then go get your driver,
its that simple.
lets pretend , its xp 32
under multi media.
sp44106.exe
in all cases when any PC fails for any reasons like this
1 thing bad, or 2.
we go to device manager,
and click view, show hidden devices
do you see anything there with yellow, red marks or errors.
we do that to see if some drivers were deleted.
or worse, a new OS installed and many are now wrong or missing.
see?
do that first. make sure all drivers on the HP page are loaded
for sure the grapics and camera , and the first 8 on the HP sites driver page,
look for a softpaq, to autoload all that.
or run the newer
HP support assistant
http://www8.hp.com/us/en/campaigns/hpsupportassistant/hpsupport.html