When you finish loading FSX with your two DVDs, there will be a notification at the end if you wish to activate FSX. If you don't activate it, then you will get about 30 minutes of flying time before it stops.
If you have tried activating FSX but it won't work, then there is a fix that is generally used. This is as follows:
- Shut down FSX completely and then run Registry Editor (press Windows key + R and type regedit and Ok).
- Expand the following registry key, but be careful when changing Registry values (you may want to back up your Registry if you are unsure):
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class{4d36e967-e325-11ce-bfc1-08002be10318}
- After you find the folder, double-click Upperfilters on the right side.
- Change the value from 0 to PartMgr (note, this is case sensitive) and delete any other word that may be next to it and click OK.
5. Close Registry Editor and reboot Computer.
- Start FSX and check whether the Activation box comes up.