The UK Copyright Statute provides that people may make backups of software, without infringing copyright. This provision retains the legality of making a copy of a computer programme in these circumstances. The other two potential restrictions are contractual and technological, as is so often the case in digital copyright. The contractual issue is dealt with easily: the same law voids any contractual bar on making backups.
Some details remain: the law only applies to computer programmes, not to the components of software, such as images and sounds, which are not computer programmes (this is a favourite point of the killjoys at the European Leisure Software Publishers Association, whose evolving webpage on the subject has had to be changed to take account of the changing case law, and occasional complaints to Trading Standards). However, even once every technological means has been taken to prevent backups, and the software has been conflated with as much copyrighted material (not being computer programmes) as possible, backups must be "necessary" to come within the scope of the provision.
In the recent Sony modchipping case, the courts examined the status of a device which afforded technological means of defeating technological restrictions on backups, as the status depended on whether there existed legally legitimate reason for defeating such restrictions. This involved considerations of the question how legal are backups of software. Because backups must be "necessary" to be legitimate, the question was also one of fact. Two arguments were put forward: backups are unnecessary due to improvements in the resilience of computer storage media, and where the vendor offers a replacement(!)
Improvements in computer storage media resilience, from floppy disks to CDs and so on, are not dispositive as media may be lost or stolen. The argument is at best a intellectually dishonest irrelevance, not least because the resilience of some media is diminished by anti-copying technology. The law says nothing of the reliability of storage media, as rightly it should not; if the law turned on such a matter, it would say so, and it does not. As to the the offer of replacements, this is a well-constructed obviation of the spirit of the law, as well as its letter: it assumes that the proprietor does not withdraw the offer to replace software on damaged, lost or stolen media, does not go bankrupt, etc.
In effect, one more area of copyright policy is being taken away from the democratically accountable legislature and subjected to private ordering by only one of the stakeholders.