blue screen after login

[jimhendrix]

I need help, I have a mac pro with os x v 10.6.4 on it, it has been working until one day I used an infected USD drive on it, then after that it has been failing to load, the problem is like this, when I power it on, it starts to load until it brings the login screen when I put my login details click login, it start loading buts on then a blue screen appears then comes back to login screen ,it keeps repeating this , I need help all my work is on this laptop please help
I tried to do command + S
then trying to fsck it says no such files or directory