IPSec Service Fails to Start - The System Cannot Find the File Specified

I recently came across a Windows Server 2003 box where no one was able to login via RDP. Additionally, Citrix was throwing an error saying "The System has reached its licenced logon limit. Please try again later"
Logging into the console revealed that various Citrix services were not started. Attempting to start these failed though because they depended on the IPSec service, which was set to disabled for some reason.
I changed the startup type to automatic and tried to start the IPSec service, but got the following error :

Event Type : Error
Event Source : Service Control Manager
Event ID : 7023
Description : The IPSEC Services service terminated with the following error:
The system cannot find the file specified.

A fix for this is often to delete the registry subkey at HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\IPSec\Policy\Local  and then rebuilding the local policy store.
When I checked, the above registry key didn't even exist on this server, which explained why IPSec wasn't able to start. As I didn't need to cover this step, I just needed to rebuild the local policy store...
To rebuild the local policy store (and recreate the above registry subkey), open a command prompt and run the following :

regsvr32 polstore.dll

Then check the IPSec service is set to automatic and restart the server.
Once my server had rebooted, IPSec started as normal, which then allowed all the Citrix services to start and full service was restored once again.