PC infected with Virus

I have a pb with 2 trojans that are entered in my pc last night and I can not delete. I use Avast which tells me that I am infected with win32: obfuscated-EJC [TROJAN], and win32.trojan-gen. I canbot surd the internet on this pc, and also it reboots every time so i better turned it off. If someone can help me that would be great. Thanks

to begin downloaded hijackthis:
once install rename the file "hijackthis.exe"
then open hijackthis and "do a system scan and a logfile"
and post the report on this forum.