Hello, I have a presario f755us that does not start up. I have tried everything on this site. My grandchildren had been using it for youtube. Then they brought it to me and it did not start. I don't know if they had dropped it or not. There are two lamps that flash and the power cord connection.

Ask them exactly what happened just before it went off or the last time they used it. May be they spilled a drink on it. A knock will leave scratches/broken screen.

F755US (about 10 years old) A LAPTOP
runs VISTA new, is it?
is the PC silent, no fan spins , no sounds at all?
take out the big battery first bottom , with latch.
do that now.
got text to screen now, fan blows air.
got logos of any kind to screen
got "Hit F10 for HP setup?" works on screen seen for 10 years every time you turn it on.?
does the F10 if prompted above.
is the line power pack AC , have damaged cables or ends?

this PC will have 3 major failers at 10 years. as all laptops do. this old. ALL
1; RTC coin cell dead. replace it.
2: main battery is bad, worse shorted run PC with no main battery NOW.
3: the CCFL back lamps so not last 10 years. unless
the laptop spent its hole life parked on a shelf turned off.

4: BAD HDD, (last) if the PC is silent say so please.
are the blink or beep codes happening?

Compatible AC Adapter for Compaq Presario F755US Laptop

I think it has a bad power adapter yielding insufficient voltage.

This system is running Vista which makes it quite dated. However, you can try the replacement supply and see what happens. Or, they coud view Utube on an inexpensive android tablet.

However, you can try the following (I am guessing you do not have the Vista disc):

To boot into the Advanced Boot Options menu, follow these steps:

1. Restart your computer
2. Press F8 as soon as your computer starts to boot, but before the Windows Vista logo appears
3. The Advanced Boot Options menu should now appear
4. Select the Repair your computer option
5. Press Enter
6. System Recovery Options should now be available (You may need to select your time, keyboard and language preferences before the list of tools is displayed)