I can't open the case of my optiplex 740, it seems to be stuck or locked., i've tried pulling it but i don't want to pull too hard because i might damage it., please help me., thanks a lot

Sounds like you are describing a binding issue with the latch.

From this video link, showing no physical lock in the latch handle hole, a good working case latch opens the cover easily.

https://m.youtube.com/watch?v=oKDzYhTfAXk#bottom-sheet

Tolerances changing on metal parts like slides can cause binding.

Sometimes a stuck case can be opened using gentle pressure, noting where you push, or tap on case around the mechanism as you put pressure on latch, trying to remember where you press in an organized way, so you don't repeat what doesn't work,
It's organized luck,
look in video how latch is constructed , turn case
To accommodate where gravity might help, small chance.

Try to turn off or pull the battery DON'T LEAVE IT ON that's the worst thing you can do if that doesn't work take it back and demand refund

lever catch on hood latch is sticking .light thump with hand ' in area of h hood catch should pop hood

there r plastic moulded locks..open with pryin with a knifed screw driver safely after unscrew all the screws

You dont' mention a brand, although I'm not sure that matters....I've never seen a filter drawer that locks, but there could be a brand I'm not familiar with that does? Anyway, it would seem that it's stuck? Try taking a butter type knife or something similiar and running it around the edge at the top to make sure you don't have something hung up there...If not, is there anyway to access the drawer from the back or underside? If there is, push from there, while someone else pulls from the front...If none of these things work or you just cannot access the back at all, call the manufacturer, as they may have another idea. Maybe this is not the first time it's happened to one of their units and they know alittle secret to get it open? You should be able to find their phone number online, but if you can't, call me and I'll find it in one of my catalogs... Susan at Restaurant Equipment Outlet, Cincinnati, Ohio, or Paul @ 888-542-5959. Thanks, Susan REO

Hello, don't try and do anything until you've looked at the manual, which is available on the Dell website.
Regards,
nicam49

turn ignition key to the left this opens the seat !

Pull starter rope wheel is Jamming against casing usually some lube n check for ware will fix it

what will not open?

dell optiplex have very tight casings, dont be afraid to use force.
I have one myself and it is a struggle to get the casing off.
as long as those 2 side buttons are pushed in just give it a good tug and hopefully it should come off.