Trojan and malware infected PC

I am currently working on cleaning a PC that has a few trojans..I could not load and anti virus or anti spyware programs. no programs can be executed, no programs can be installed, no access to regedit . I ran a scan from security.symantec.com that identified the infected files which I deleted. Every time I try to install a new program or run any existing one a process named spool.exe starts, how do I clean this PC? Is there a solution without reimaging?