Many companies have a heavily customised IT environment which is very unlike a home setup. Any new recruit to a Helpdesk will need several weeks (if not months) of training in the internal systems and infrastructure before they're permitted to take calls from users. Don't let your lack of knowledge phase you.
As long as you're applying for an entry-level Helpdesk job, then I see no problem with talking about being interested in resolving your own IT issues and being keen to expand into the professional field. If you try to blag that you're up to a corporate environment based on what you've done to home computers, then you'll be spotted a mile off and probably won't even make the interview.
For an IT Helpdesk, there are key traits that you need to put across:
- A positive and frendly telephone manner. It might sound daft for an IT specialist, but that will be your main point of contact with users. If you come across badly then you just won't be able to do the job. When I recruited for Helpdesks, our first filter for prospective candidates was to give them a telephone interview before inviting them for a face-to-face interview.
- The ability to stay calm under pressure. People who call Helpdesks are stressed, angry and can't do their jobs because something's gone wrong. They will talk to you as though you caused the problem. You can't take it personally - that's just the psychology of the situation. And you have to be able to handle it day in, day out.
- The ability to listen and take in information. Another thing that sounds obvious, but if you fall into the trap of just automatically telling every caller to "switch it off and back on again" without properly checking the symptoms of their problem, you can waste valuable business time and possibly send second-line support technicians off on a wild goose chase. Both of these will cost money.
- The ability to learn new technologies and concepts fast and be able to apply them. Companies will be upgrading/replaceing systems and hardware on a regular basis. You'll always be expected to learn and support something new, so your induction period will just be the start of a never-ending learning curve.
- The ability to speak "user" plain English and translate that into the type of technical details that second-line support teams need to resolve the issue.
When you first start on a Helpdesk, your existing technical knowledge is probably your least important attribute. An IT Helpdesk is certainly a good springboard to move into more specialist hands-on IT support, if that's something you're considering.