An old system? How old is the hard disk inside the computer if you don't mind me asking? And is it an HDD or SSD?
The older a hard disk gets, the more bad sectors it forms which generally slow down read operations in any program. It could make reads take several seconds to complete for instance. You can't even kill a program in linux with SIGKILL while it's blocked by an I/O read or write.
I'm not sure if SSDs have this sort of problem but I don't think there is one in your computer.