sudden changes in computer function and capability

I recently purchased a used HP probook primarily for the reason of running pro tools mp9. the laptop's specs are easily more than the system requirements for the program, and it worked fine. I share a house with several musicians, and had an understanding that they would only use the computer for recording. one morning, when I looked to see what might have been recorded (I would set up the program, which requires an ilok, and an interface)this particular morning, the program was closed, and my desktop was scrambled, and when I went to restart the computer, it stopped at a black screen with a blinking cursor in the upper left hand corner. I had to manually shut off the machine with it's power switch and turn it back on. when I loaded the pro tools program, I would get an "error 9073-can't write to drive fast enough-defrag your drive" I don't know that this is malware related, but I am suspicious after finding the computer online. additionally, the wireless router at the time had no security set up. I subsequently reset and set up wpac on the router, but again, a suspicious thing in my mind. assuming that this is malware related, is it possible for me to completely disable the wireless modem so people can't use my machine online? also, I couldn't figure out how to upload the mbam log from malwarebytes, although it showed no malicious items in the scan, I know you still wanted it.

 

many thanks! I will do as you suggest