1. There cannot be a hard drive size limit for a computer. It depends on OS.
2. Neither there cannot be a 'support' decision made be its hard drive size.
Above are nonsense responses and I think the ones you talked to are simply hired people who don't have knowledge on computers. You should continuously ask for a tech guy (who really knows stuffs) don't even waste time on simple representatives who responds with ignorance.
MrLinux is right.