If you are getting errors when performing a system scan on the NTFS file system partition of your Windows hard drive and cannot access your hard drive partition it may be due to cross linked files and lost cluster issues. Lost clusters are not that uncommon due to a system being shut down the wrong way or an application crash. This keeps partial files behind, which are shown as lost clusters because the files were not completed properly. This can sometimes have the need for a NTFS data recovery.
To fix this issue be sure that you do not have any viruses by doing a system scan and check your hard drive by utilizing a Chkdsk.exe utility. Always shut down your computer properly by using the start button instead of pushing the button on the CPU. You may have to shut down your computer this way from time to time but do not make it a habit because the issues it can cause.
Check for resource conflicts and instability issues with the operation system you are using such as XP, Vista or Windows 7. If you have recently installed new hardware or software try uninstalling it to see if the issue clears up. If it does, reinstall it and try again. If you continue to have issues the software or hardware may not be compatible.
If none of the above works you may have to reformat your hard drive and reinstall the operating system. There is the option of NTFS file recovery once you are done since this will remove your partitions.
To recover the lost files you will need to find data recovery software from a reputable third party online. One such vendor is Stellar Phoenix NTFS Data Recovery, which effectively recovers lost hard drive partitions on Windows. Not only does it recover lost data but also NTFS5 and NTFS file system partitions that may have been irretrievable.