I'd suggest you try to run your manufacturer's diagnostic utility, if avaliable. Another popular option would be booting from a Linux boot CD or DVD, you should search the internet for details about this solution. I would also suggest you try the drive with another PC or laptop to see if files will be accessible. Also – have you tried defragmenting the drive? If the problem is indeed not enough free space, it may help. If you manage to gain access to the drive at any point I'd recommend you do a backup of the data.
You can also try running a data recovery software or, if everything else fails, in case your data is very important - consider a data recovery company.
Hope I was helpful, Citizen_WD
message edited by Citizen_WD