PROTIP:
In that situation, it's best to ask a mod to lock the thread or to just ask everyone not to post in it and tell them about the new thread.
When you delete a long thread, people will get upset (as has happened here) because their post count will go down and some valuable information might be lost (this is probably why you can't delete threads in the technical forums). Deleting a thread without a very good reason might be seen as rude or childish, especially as it's something often done by trolls or attention whores. I'm sure that you're not either of those, but they're generally the kind of people who delete big threads.