OK I will need to try and locate some files and see if they are in the right place

Prior to this problem what happened ? Were you running a malware removal programme or something like that ?

If this fails I may need to run a programme from a USB drive to locate and then run one of your system restore points - do you have a USB drive ?

Run OTL and copy the following into the custom scans box and then press run scan

/md5start
lsass.*
/md5stop