If you're looking to change the actual registry value from hexadecimal to decimal I don't think that is possible as whatever program or service is using that value is going to continue to interpret it as hexadecimal. You can likely decipher what that that hex value actually means though. If you have a base understanding of hexadecimal then it should be easy to determine that 0x19 is equal to 1x16+9= 25 in decimal. 

Hi Kevin,

Can you describe the use case for the scenario you presented? 
As described by Matt above, if you are looking to change the actual registry entry, it is likely that the program accessing it is expecting a hexadecimal value - therefore entering it as a decimal value may cause issues. 

Regards, 
- G