I had a new email in my Hotmail inbox this morning. In fact I had 26, with subject messages like "I'm lonely, come play with me" and "Take advantage of low rates now". Others came from companies with a clear understanding of my geography - a smooth, targeted marketing campaign offered "Free chocolate with a dozen roses for $29", or bizarrely, "Somos los unicos".

I ignored them all - except for one from Hotmail itself.

Usually I'll turn a blind eye to emails from Hotmail Member Services. But this one, with the subject "Your account size is too large ... Upgrade now!" seemed urgent. It said I had allowed my account to exceed its 2MB storage limit and I therefore had to upgrade.

Whether or not this sudden influx of spam emails had helped to turn me into an offender was by the by: Hotmail was warning me that unless I deleted some of my emails, someone - in fact, the spookily named Hotmail Janitor - would do it for me.

I was given two options: either reduce my storage limit or pay £19.99 a year for an extra 8MB. So it was one option really, because there is no way I would be prepared to pay 20 quid. And this is why.

If you think of the internet as an information superhighway, it does not take much of an imaginative leap to compare using the internet to driving a car. You buy a PC, much like you pay for your car. You sign up to an ISP, much as you pay your road tax, and you fill up with petrol, or pay your monthly subscription fee or call charges. That's all fine.

While "driving" you might stop at a service station and have a look at the cassette tapes. Being constantly on the look-out for something amusing to share with your friends, you buy a copy of Tibetan monks sing classic movie soundtracks of the 1970s. You figure that if nothing else, a version of the theme from Taxi Driver - complete with a broken-English rendition of the "one day a real rain will come" speech over a chanted rendition of the score - will have great kitsch value.

Then you need somewhere to store the tape, so you move over to throw it into the glove compartment. However, when you try to open the door a message sings out: "Your glove box is too full. Unless you pay a fee you will not be able to store anything else in here."

"But," you cry, "I've only got an old map of Milton Keynes in there, and a pair of sunglasses to shame Elton John. This can't be right."

"Well, it is," answers the glove box. "I'm full and unless you give me £19.99 per year, you won't be sticking any more rubbish in me."

"Fine," you retort. "There are plenty of other places for me to store my things. I'm moving on and you can keep the map and the glasses. I hope you choke on them." With that, you put the tape in the door compartment and drive off.

It won't happen in a car, but if you make people pay for something online that previously was free, they will go off it fast. Why then does Hotmail think anyone will pay for extra storage? Given that on a daily basis my inbox throws up more spam than a roomful of schoolboys with food poisoning, and there are many other free email providers out there, I know I won't be shelling out.