Hard Drive C system disappeared

[Breckon]

Yesterday evening my antivirus has discovered a trojan.J which has made a bad handling and patatra virus or trojan was installed. The problem is that I can no longer have access to the System C drive and I can not see it either. The PC turns off and even when I am accessing other records, internet ect ... . What do I do? (I checked with antivir and spybot and it did not work)
Thank you in advance for your reply

[Zachary]

if you can do this=> go in start, workstation, (right click), manage, Disk Management. you do not always check your C drive?

[Big Fish]

click on the link to download Hijackthis

http://www.trendsecure.com/portal/en...hijackthis.php

Save HJTInstall.exe on your desktop.

Double-click on HJTInstall.exe to launch the program.

By default, it will move there:
C:\Program Files\Trend Micro\HijackThis

Accepts the license by clicking "I Accept"

Choose the option "Do a system scan and save a log file"

Click on "Save log" to save the report, which will open with notepad

Click on "Edit -> Select All", then "Edition -> Copy to copy the entire contents of the report here