how to compare 2 .exe line by line?

[TQN]

You can use IDA to deassembler two exe file, choose output to ASM file in File menu, and compare two asm file with WinMerge or UltraEdit...
Regards

[SofTROOP]

WinHex can compare 2 files and generates a list file which list all differences with their offsets, so you can easily track to the position in Olly for further research.

[britedream]

Hi jayjay,
I may misunderstood you, if you mean compare the assembly , then I think if you run trace to log to file for both files and use compare it , it should do it.