So long as you are getting your job done I don't see the problem.
I had this argument with my ex when she wanted me to do something during working hours and I refused becase it was during working hours.
She said that my empoyer "didn't OWN me!"
In a way, yes they do! By paying me a salary (however pathetic it might be) they are buying my time five days a week from 9 to 5 with an hour off for lunch.
It has also been the case, several times, that a personal use of the company computer (not mine I am glad to say) for an internet search for something or other has resulted in the infection of the company system with a virus of one sort or another. It is also the case these days that most employment contracts specifically forbid use of company computers for personal business for this very reason.
With the increasing sophistication of mobile 'phones who needs to use the company computer any longer for personal business anyway?