detect rootkit and got to restart but no vain

hello.
i have a computer that resonds very weird. and i cant do lot of things (when downloading a file - it download a different file, registry edit, watching internet video, change desktop wallpaper, .... )
the big problem is that i don't have phisical access to the computer - only VIA VNC (the computer is in Hungary, and i'm in another country).

i managed to download Combofix and copy him to my client via Skype (!!!) :confused

when i finally managed to run Combofix, it said something like
"Combofix has detected presence of a Rootkit activity, and will restart the computer". and immidiatly, reboot.
afterwards, the computer starts and all my client can see is the mouse and a black background. the mouse cursor is on "sand-clock" mode for more than a hour and then he gets normal desktop. but combofix doesnt work.

i tried all this for about 10 times before tried to post. so please, any idea will be very appriciated.
(if someone is kind enough - i let him the ip and password for VNC access)

thank you everyone !
:wave

 

thank you !
i used Malwarebytes' Anti-Malware and it found few things and remove it !