Well i just encounter slight prob with my itunes today.. Error says " backup files cannot be saved on the computer " delete all my backup through itunes doesnt solve.. Cant delete the folder manually as it says "its being used by other program"

so now im stuck..im planning to update to coming 4.2 but i want to backup evry single thing first..so frst ques..how to solve above matters?? N secondly, ive read some good backup apps in cydia..can somebody tell me what is the best backup software.. How it works n how to use it..thanks!!