Currently, the "Hardware" tag is disabled:
However, things such as "Hardware-failure" are allowed.
The reason the tag was closed (based on my research) is that it lead to quite a bit of shopping questions. Shopping questions should remain unallowed however there are plenty of valid uses for this: Example - Yes, the question is a duplicate however the best tag I could use for it was "Laptop", and that isn't a very good tag.
Again, this should only be used for hardware problems (not necessarily failures, just problems). The rule about no shopping would still apply.