Right now, the account on the computer is in your friend’s name. You cannot perform a reset without her password because Windows will not allow it. She can opt to reset her password so you can log in, but she will need to do that herself.
Another option is to wipe that hard drive clean and reinstall Windows in your name. This will require that you first download a Windows image file and either burn it to a bootable DVD or create a bootable USB drive. The link to download the Winodows image is below:
Second, attach the USB or DVD to a port on the computer. Third, enter the computer’s BIOS by turning on the computer and quickly pressing the F2 key repeatedly before the Acer logo appears. In the BIOS, poke around until you find the option to boot from the DVD or USB, and make sure that it is first on the list of devices that the computer will boot from. Save your changes and exit BIOS.
The computer will restart and boot from the DVD or USB. Follow the prompts to reinstall Windows.