The process cannot access the file

Hi all

while i create a text file it gives me error on the line

sw = File.CreateText(fileName); 

that

File Creation failed. Reason is as follows The process cannot access the file 'C:\Documents and Settings\191128\My Documents\Log Call\UsersOnly\test.txt' because it is being used by another process. 

There is a file already present in 'C:\Documents and Settings\191128\My Documents\Log Call\UsersOnly location ,the page load executes successfully but , when i click the submit button , it gives me error.

 
protected void Page_Load(object Go to the complete details ...