I must have made a mistake when trying to delete some information from my C-disk (C-disk contains program and D-disk contains data). When I then try to start Lightroom, I get the message "lightroom.exe - system error. Code execution cannot continue as mfc110u.dll cannot be found". But I can find that file in 2 places. Confusing.
I have Lightroom 6 on a CD and I try to make a restart, but then a 24 digit code is required. I have checked the box but there is no such number on it. Is my CD too old?
I believe that 24 digit code is the serial number that accompanied your disk. It was packaged with it. The first four numbers were 1160. You might check your account. If you registered your copy of Lightroom promptly the serial number should be listed in your account information.
When I earlier got Adobe products, I have got them in a plastic box and with the 24 digits on the back side. This Lightroom 6 I have got in a paperbox with this information on the back side. I have used this version during a number of years, but due to some mistake, I have lost it.
The serial number is not printed on something like that. It is usually on a small slip of paper included inside the disc jacket. It is six groups of four numbers, the first four are always 1160. If you registered your product with Adobe then it's possible you can retrieve the serial number from your account information online. If not then I don't know how to help you. That serial number is key to activating Lightroom 6.
Lightroom 6 is really quite old now. I know, you don't want to go to the subscription model. But I think it's only time until operating systems progress to the point that what you have been using isn't going to be supported anyway. Lightroom Classic has moved on and offers so much more than what Lightroom 6 was that I believe you are cheating yourself by trying to stay with such outdated software. But if you can find your serial number and want to try to keep using it, the choice is yours. There really isn't anything more we can do for you.
What to do? Your recommendation? Should I buy a new version of Lightroom 6? If yes, which one?
You cannot 'buy' Lightroom-6 whatsoever!
Without a Serial Key you are 'stuck'!
You can subscribe on an annual plan to the 'Photography Plan (20Gb)' that includes Lightroom-Classic v10 (the latest version of your v6), Photoshop, etc. (NOT the 'Lightroom Plan 1Tb' !!)
Without your serial number, there is no other solution. Adobe does not sell any standalone version of Lightroom anymore. Lightroom Classic is the replacement for Lightroom 6. It is available by subscription only and comes in the photography plan. The cost is $9.99/month, and includes Lightroom Classic, Photoshop, Bridge, Lightroom (the cloud version) with 20 GB of cloud storage. The cloud version appeals to many users, the feature set is quite different from Lightroom Classic. Lightroom Classic has improved substantially since Lightroom 6.
It seems that some shy away from it because it is part of the cloud program. But don't let that fool you. When you subscribe you install the creative cloud application manager. That allows you to install on your computer the applications that you have subscribed to, and enables you to keep them updated. Lightroom Classic installs locally on your computer and runs locally just like Lightroom 6 has been running on your computer. It will upgrade the catalog you have been using and will enable you to continue working without losing any of your previous work.
This will be my solution. I have to accept that I have made a mistake and lost Lightroom. I have all pictures stored in files, so they are not lost. I also have them on my back-up disk.
Thanks for your help.