Meghanmar,
If you would just like to stream data from the COM port and log it to a text file, assuming you are using the Windows operating system you could use HyperTerminal (a program that comes with Windows). It is available on the Start Menu at Programs » Accessories » Communications » HyperTerminal. Once you set up your session to the COM port, go to the "Transfer" menu option and select "Capture Text". It will prompt you for a location and file name for the text file. Afterwards, all received data will be logged to the text file. You can go back to the same menu location and select "Capture Text » Stop" when you have received all of the data of interest.
If you need to do a more complex acquisiton, you would likely need to program it using a language such as LabVIEW or CVI.
Sincerely,
RossC