Hi there damienahl,
You really need to provide some more information on the issue. Is the drive internal or external one? Is this your OS drive?(in case it is you may need to attach it to another system)
You can start with something simple as just attaching the drive with different cables(USB if external and SATA and power ones if internal) to a different port.
After that, you can go to Disk Management and see whether and how is the drive recognized over there.
In case it is not, then it has most probably failed.
In case it is, but has damaged partitions or a file system, you may need to use some data recovery software.
I guess you can try testing it as well:
http/www.tomshardware.co.uk/forum/282651-32-best-diagnostic-testing-utility
Cheers,
D_Know_WD