Sure, give the new kid and his MCSE power over the AS/400. What could possibly go wrong?

Who, Me? Dear reader, is that you? Can it be? Why, that can only mean one thing: that yet again it is Monday, and therefore time for an instalment of Who, Me? – the column in which Reg readers confess the times they really didn't get things quite right.

This week meet "Fred", who some years ago landed his first real IT job fresh from a bootcamp at which he earned the Microsoft Certified Systems Engineer certification. The job was with a big construction company that operated over multiple sites – quite an opportunity for a young up-and-comer with more enthusiasm than experience.

This job came with a 90-day probation period, so Fred was being particularly diligent. Within a week he impressed the boss with "a miraculous IDE hard drive recovery involving swapping out the bad controller card with a working duplicate one."

We're not sure that sounds particularly "miraculous" but maybe you had to be there. The boss's praise filled Fred with confidence.

A short while later, a problem with the AS/400 midrange box emerged: tape backups were not going through as they should. As the AS/400 is an IBM box this was not a job for the new kid with a still-wet Microsoft credential. But Fred's bosses saw it as a learning experience, so he was asked to watch while a qualified tech did the job.

That old hand said the drive would have to be removed and replaced with a working unit, so the AS/400 would have to be powered down while he extracted the relevant hardware. The boss went to the phone, called the front desk, and told the receptionist to make an announcement over the PA: all users had to close their work and log off. Fred watched closely.

All went well.

• Polishing off a printer with a flourish revealed not to be best practice
• Lesson 1: Keep your mind on the ... why aren't the servers making any noise?
• The price of freedom turned out to be an afternoon of tech panic
• Techie's quick cure for a curious conflict caused a huge headache

A few days later the technician returned with the replacement tape drive, and informed Fred that the server would again need to be powered down while the new unit was installed.

This time, however, the boss was at one of the other sites hundreds of kilometers away, so could not make the call to reception. Fred, young go-getter that he was, took it upon himself to make the crucial call and ask everyone to close their work and log off.

After a few minutes, it was deemed safe to proceed, and the technician powered down the mainframe.

The the phone rang. It was the boss, over at the other site, wondering what had happened to the AS/400. He was … let's say … surprised to learn that it had been shut down on Fred's say-so.

It had not occurred to Fred that workers at other sites might be logged into the same mainframe. Nor that they might need to be informed that they were in imminent danger of losing work. Nor, apparently, that a fresh recruit still on probation probably doesn't have the authority to say it's OK to shut down the enterprise server.

Needless to say, people lost hours worth of work. Given one of those people was the boss, you can imagine how it ended for young Fred. At least it was a learning experience.

Has a bit of enthusiastic over-reach ever cost you a job? Don't worry, it's happened to a lot of us. Tell us all about your experience in an email to Who, Me? and we'll commiserate together.