Have had to reset 3 cmos in 2 weeks

I’m having problems with my home computers. I have 3-one newly built a week ago. All three run XP. In the last two weeks, all three have quit working. When I reset the PS switch, I got a short burst of fan, but then nothing. Resetting the cmos worked. But I don’t want to have this issue continually. I live in an older part of town, and was wondering if the power grid could be causing the problem? I leave them running 24/7 and have never had this kind of issue before.