Dells used to be very good indeed. Not really upgradeable but they were designed for corporate use - Easy but non standard component replacement and scrapped after a year or so. I have a slightly later Dell (An XPS 500) which is still in use and cannot be broken! It weighs a ton and if it could be kicked from here to Timbuctoo and back it would still function without problem.

In comparison, the Dells I've seen of late are little more than ugly black sardine cans with a bunch of USB ports hanging from every orifice. I avoid working on them whenever possible.