When i turn on my computer(an hp pavalion a1720n),it seems fine, i bought it refurbished recently from a computer store in mt. Vernon. After opening up the case to try to install a floppy disk drive,realizing it didnt fit the plugs, and giving up, i turned on my computer a few days later to see it load at the windows logo, after that finished, it became stuck at the small waiting period between the windows screen and the login screen, i can move my mouse, but i have to turn off the computer via the power button. All safe modes dont work. Pressing f11 at the boot menu doesnt work. And im stuck at that. Please help!