Now that HMV has gone the way of Jessops and placed itself in administration, aside from the worries faced by the staff of HMV those with gift vouchers will also be worried.
As of today HMV have stopped accepting HMV gift vouchers. Whilst the administrators may choose to accept them at some stage in the future, there is no guarantee that they will. Additionally, if any part of the chain is sold to a third party the new owner is under no legal obligation to accept the gift vouchers.
Which? recommend that those holding gift vouchers in failed chains such as Jessops and HMV write to the administrators to ask for a refund (a process that offers no guarantees and may well take at least 12 months). Which? have a helpful Q&A section wrt failed retailers, which also has a link to a template for a letter asking for a refund of gift vouchers held.
Ironically, not everyone has done so badly out of the failure of HMV. A number of companies/individuals heavily shorted HMV in the days running up to its demise in the hope of making a killing out of its failure.