What may be a heap of smelly mud and rubbish to many is a field of dreams to others – including the hard drive owner James Howells.
The drive measures around six inches by three inches and is less than an inch thick.
The landfill site is about 100 yards by 50 yards.
The treasure on the hard drive is 7500 encrypted Bitcoins, the virtual currency that can only be unlocked on a computer.
Howells bought them five years ago when they worthless. Today they are worth $1,000 each, which makes the computer drive worth more than its weight in gold.
At current exchange rates the Bitcoin are worth $7.5 million – equivalent to £3.6 million.
The loser explained that the drive was kept in a drawer for years and thrown away when he recently moved house.
The landfill site is at Newport, South Wales, and now news of the loss has leaked out, the local council is expecting a rush of get-rich-quick prospectors to turn up to sift through the piles of garbage to find the Bitcoin bonanza.
“The manager is sympathetic and took me on a tour of the site,” said Howells. “It’s enormous and at first I thought I had no chance of finding the hard drive.
“At the rate the rubbish piles up, it could be at least three feet down and more is added every day and the stench is awful.”
Forensic searches of landfill sites of a similar size have involved 20 police with dogs and digging machinery, according to the local council.
“I have not got the money to shell out for that sort of search without knowing the disk drive will definitely be recovered,” said Howells.
Bitcoin is a virtual currency that can only be accessed through encryption online.
The currency was released in 2009 and is used online to buy goods or services.
The Winklevoss brothers, who also invested in Facebook, have a large stake in Bitcoin and are bidding to make the currency an alternative to real rather than virtual money.
A controlled amount of Bitcoin is in distribution.
The currency is not regulated by any central bank and is subject to free market exchange rates.
Many, including the US Treasury, have criticised the currency as a means for criminals and terrorists to finance operations without detection, although German banks will exchange Bitcoin for euros over the counter.