You can set any default text in QTP by the following method.
1. Open the dat folder in the following path:
    
C:/ProgramFiles/MercuryInteractive/QuickTestProfessional/dat

2. Create a notepad in that folder.

3. Enter the text you want get displayed in QTP by default.
Use single quotes "'" before the text so as to make it a 
comment.
eg., 'Good morning

4. Save the file as "Actiontemplate.mst"
That's it. Whenever you open the QTP you can see the text 
added in Actiontemplate by default.

You can set any default text in QTP by the following method.
1. Open the dat folder in the following path:
    
C:/ProgramFiles/MercuryInteractive/QuickTestProfessional/dat

2. Create a notepad in that folder.
3. Type the text at "Good morning"
4. Save the file as "Actiontemplate.mst"
That's it. Whenever you open the QTP you can see the text 
added in Actiontemplate by default.

I have create actiontemplate.mst in dat folder, however 
could not see when I opened QTP. Where exactly in qtp does 
it display?

HI Swapna,

The answer given by Chinna is correct.It working fine.
Create an Actiontemplate.mst file in the above mentioned 
path, That is where u installed your QTP.
Now Open QTP application, When u can see the whatever text 
u have written in the Actiontemplate.mst file.

Hi Could some one explain me how to create the notepad in
Dat folder.. Give me with an example please

Hi Swapna,
What Chinna told is correct. You might have mistake while 
saving it..
i.e while saving in Save window, pls select Save as type as
All Files. You will get it...

Hi Swapna,

The above script is correct. It works fine. 
I have encountered the same problem, but the problem is not 
with the script. 
As per the script i have created a notepad but while 
renaming i have selected someother notepad file. The script 
didnt work. So For Crossverification i have opened the 
Actiontemplate.mst file in notepad where i was expecting my 
default test eg: Good morning but i could not find the 
text. Then i recognized i have done a mistake and edit the 
same file and entered the text and saved it.
I hope you would have done the same. It works for me now.. 
Pls let me know if you still could not figure the issue