I have carried stock PCs on long bike trips for 20+ years:
- carried 286 Sharp across USA in '92
- carried HP Omnibook 800 across Canada in '97
- carried Sony Vaio around Australia in '01 and different one across Russia in '07
- carried these and other laptop PCs
I've has disk drives go bad (in Vaio in Australia) and broken screens not on bike trips.

However, in general reliability of stock laptops has been remarkably good. Given newer trends to solid state drives and different form factors like tablets, I don't see that I would carry the extra weight or pay extra cost for a specially rugged-ized PC. Instead, make sure everything is packed in waterproof casing and sometimes add some foam for shock. I also make sure my sensitive data is saved on USB or other secondary drive (sometimes on two such drives) and consider it good enough.