I just got a HP4520s probook... while doing some installations of software, suddenly the cursor froze in the centre and an orage light appeared on the touch pad. I google and tried all the suggestions given ie function key with F7, F8, F9 and all others. I can't find the button that is supposed to turn on/off the touchpad... can u help?

Sometimes there's a mouse pic on one of your function keys to local/unlock pad. Hold the function key while tapping the f key once to unlock

Do you have a micro USB device plugged in. Some touch pads automatically disable if you plug in any type of USB mouse device. You can also go into the device manager and uninstall the pad (do not use the delete/remove drivers option), then reboot. Windows will reinstall the device, and sometimes that fixes issues. Or do like it do and use a wireless mouse. I hate those touch pads anyway. ;-)

please select boot device from bios

fast duble tap in left upper corner of tachpad can ON and OFF it

The windows files are corrupted or the hard drive has issues, load cd installation disc if available, if that fails have the hardware checked for possible replacement.

Try
Start > Control Panel > Display > Calibrate Color > How do I calibrate My Display >
Just step through this carefully and hopefully your colors will be corrected.

I have a 4520s but never have done this.

You might have disabled the touchpad accidentally. If the touchpad is disabled it is indicated by a yellow LED on upper left corner of the touchpad and when the TouchPad is active, the light is off.
To turn the TouchPad on, quickly double-tap the TouchPad off indicator (the yello LED).

Hope it helps!
CreativeTECH

Acer has a recovery icon in desktop no need to back up a new PC.....But i would advise u take it back...that freezing is an error in the OS system

the acer has a driver and software restore program on your desktop, I suggest you re install the driver for the mouse pad, you may have to use an external usb mouse to do it. try that

it is absolutely broken even u can click right and left but the red light is off it is like half dead machine, i advise u get another one...