how long does it take to reset a ipod touch 4g to factory settings?

i clicked reset on my ipod cause it wasnt propperly downloading songs from itunes, nor would it update the ios, im not sure why. but its been about 18 hrs sence i clicked reset, ive had it plugged into my comp for the power source, all its doing is the lil loading circle, it still moves as i type, just in the lil circle. if any1 can please help me im not sure what to do, ive heard u can mess it up if u dont take propper steps in this situation😕