That's one of those "all in one" PCs where everything is built into the LCD monitor case. Guts wise, it's a laptop. I'm typing this right now on a 4-year old Lenovo T400 lappy with a C2D P8600 (2.4GHz). HW Monitor is showing temps spiking up to 50C under load (idling around 30c). Indoor temp is about 20C. But you are still well within the maximum thermal range of that chip.
Like the other guy said, you likely have dust build-up in the cooling fan and heat sink. Not sure how easy it is to work on those all-in-ones, but at the very least I would blow out the air intake and exhaust ports. About once a year I disassemble my laptops and PCs and completely clean them out.
People are really surprised how dusty the inside of a PC or laptop can get without routine maintenance. We have to change oil and air filters in our cars to keep them running in top shape, so the same relative PM (preventative maintenance) needs to be done for computers (and gaming consoles).