Ask youself what it is you REALLY like about IT. You say you have a passion for computers - ask yourself is that for the computers themselves or the applications thereof? You've worked a Helpdesk (well, done, I couldn't have!) so you obviously have some interest in solving problems - does that extend to providing solutions in the first place?
Why am I asking all these questions? Well, it is a truism that if you want to progress to the higher echelons of a company, you should be associated with the product line - you usually can't do it in a service department and hit some kind of "glass ceiling". If it truly is the computers that inspire you, I would seriously suggest you consider a computer manufacturer, where you can be associated with the product line. As well as the big names you will already know, there are many smaller companies doing really exciting stuff. Get yourself along to a trade show and take a look around - it will be an eyeopener. Think maybe Development or Sales Support?
But if it's the application of computers that inspire you, go with an end user company, preferably one with a progressive business outlook in a field that also interests you - technology of some sort would be an obvious choice. If you can get a general introduction to all aspects of their IT operation, take a careful look at what really drives you and move in that direction.
Hope this may give some thoughts. Good Luck!