Instead, she was left shocked and frightened by the contents, fearing she had been caught up in some gangland arms deal.
The box contained a Heckler and Koch assault rifle, which was supposed to have gone to a police headquarters two miles away.
It went astray when someone at the suppliers got the final letter of the postcode wrong.
Mrs Roots called police and two armed officers arrived 'within minutes' to collect the gun.
Dorset police, who have apologised several times, assured Mrs Roots that it could not fire bullets.
It had been converted to produce an infrared beam for training exercises at their headquarters in Winfrith, near Dorchester.
But 55-year- old Mrs Roots, who lives in Winfrith Heath, wants an investigation.
She said: 'I couldn't believe my eyes. I was petrified and didn't dare touch it in case it went off.
'You just don't expect something like that to be sent by a courier, as if it was a Christmas gift or something for the house.
'A gun like this would be worth a lot. I'm sure it could be converted to shoot live rounds or used as a threat.'
She is also less than happy with the efficiency of the courier service.
Mrs Roots said: 'My home is a smallholding with fields, caravans, holiday cottages and a horse-drawn carriage that I use for weddings. There's no way you could confuse it with police headquarters.'
She added: 'The Government gets all hot under the collar when a computer goes missing. But something like this is potentially even more serious.
'How it can happen in this age of supposedly tight anti-terror security and high gun crime is beyond comprehension.'
Dorset police said that having a courier deliver the gun did not break any rules.
Assistant chief constable Adrian Whiting said: 'Although it might look like the real thing, the item isn't actually a firearm and it doesn't fire ammunition.
'It is not subject to any firearms controls other than that it couldn't be lawfully sold to someone under 18.
'Yes, if somebody wanted to misuse it and pretend it was real, then it could be quite a distressing item.
'Real firearms are transported by hand without the use of a courier.'
Police are talking to the supplier, which has not been named, to ensure the mistake is not repeated.
