To print 
Interleaved 25 barcode in Crystal Reports, what you need is Barcodesoft UFL (User Function Library) and 
Interleaved 2of5 barcode font.
    1. Open DOS prompt.
    If you are using Windows Vista or Windows 7, please Open DOS prompt as administrator.
    Go to the following folder
    CD  C:\Program Files (x86)\Common Files\Barcodesoft\FontUtil
    Type in the following DOS command to register crUFLbcs.dll
    
regsvr32 crUFLbcs.dll
     
    If registration fails, please use the following DOS command to register it.
    Regtlibv12 is a utility of Windows .NET Framework 2.0.
    
Regtlibv12  _cruflbcs.tlb
    2. Open your crystal report. Right click Formula Fields, choose "New..." from the context menu.
    Type in 
"Interleaved 25" in the Name textbox, then click "Use Editor".
    
 
    3. 	Double click "BCSLinearI25" function from Visual Basic UFLs list as shown.
    
 
    Then type in the database field as parameter.
    
 
    Now click "Save" button to save the formula field.
    4. Drag and drop the formula field in your crystal report design view.
    5. Right click formula field and choose "Format Field" from context menu. Then choose "I25mHr" as font typeface. You will see 
Interleaved 2of5 barcode.