Thanks for your replies. I found the reason. It is a careless mistake. A debug message was included into the program:<

Sunny

>>Does anyone know vfp5.0 with sp3 installed will make the compiled program larger than before?
>>
>>Before I installed sp3, my compiled program was about 2.5M, but now, I compiled it normally with sp3. The size of the compiled program was large than 6M!
>>
>>Sunny
>
>Sunny,
>
>Open the databsaes in the designer and choose Cleanup database from the databse menu. Use each VCX\SCX in the command window as a dbf and pack them;
>
> USE MyVcx.vcx EXCLUSIVE
> PACK
> USE MyScreen.SCX EXCLUSIVE
> PACK
> USE
>
>Then build the exe and see what size it is.