Mining with low spec computers can indeed be a bit challenging. I've tried it myself, and let me tell you, it's not always smooth sailing. But here's the thing: it's not impossible either. Sure, you might not get the same results as someone with a powerful setup, but if you're patient and willing to tinker around, you can still make it work. Just keep in mind the power consumption and potential return on investment, so you can manage your expectations.
What difference does it make on which PC to start mining?
On a weak PC, the electricity bill will be more than the profit from mining, on a powerful PC there will be a very long payback period. In good moments of the market, it is profitable to mine on a PC, when the profit from the processor and video card gives 4-5 dollars per day, but now there is no such income.