I have ran about 5 virus scans, finds 4 things, it fixes them but the problem still remains, Malware Bytes which usually helps a great deal comes up with nothing, and Trojan Remover tells me what I already know about the userinit.exe file, and says it can't fix the file and i need to do it manually, so I have even replaced the userinit.exe file with a working one from this laptop (My girlfriends) but the problem still remains! Grrrrrrr!!! 
Help please anyone, I have fixed many a PC before from hardware to software, and even build them in my spare time as a hobby, so I know my way around the inside and out of a computer but this has stumped me, what's puzzling me is why i cannot boot from CD!
Any help would be great! Thanks