In NYC there can always be something New and Unknown.
Computers' specialty stores that are open late like MicroCenter, Fry's etc., do not have sores in NYC.
In general the 24/7 phenomenon is majorly down in the City (people get home late from work and shop online, while most food is delivered to Home).
As for Computer stores! Almost all the small computers' store disappeared.
There is few Apple and Microsoft Stores, as well as the Computers' Dep. of Best Buy Staples and the Like.
Some small computer repair shops offer on-call service 24/7. Depending on the neighborhood you can Google for one.
Example -
http://www.laptopmd.com/business/emergency-service/
Or, MicroCenter has a store out od the City in Flushing that is opened until 9pm.
However, you will need to Drive out of the City for about 25-35 minutes (off rush hour and might cost Tunnel Bridge tolls) to get there.