do u mean trials? if so then there are two types
1-time trials where the program is disabled after a certain amount of time; and
2- limited trials which have limitation that you can access.
for time trials you can use the ollydbg which shifts
The first step is to launch Olly (the debugger).
Open the program you want to crack (cracking will be easier if the program is already expired). Olly will do some processing and analyzing, then display the code.
The very first thing you want to do is right-click the code and select "Search for" -> "All intermodular calls".
A window should pop up and show a big list of functions. These are all of the APIs that Olly found in the code.
Towards the top of the window, there is a row of that says "Address | Disassembly | Destination".
Click destination, so we can sort the APIs by name. Scroll down until you find a function called "GetSystemTime". (If there are several, you will have to follow the next steps for each one.)
Click it and press F2. This will set a breakpoint so the program will automatically be paused when GetSystemTime is called.
Press F9 to run the program. The program should pause before it can show you a dialog box notifying you that the trial is expired. If that happens, then go back to Olly, and press CTRL+F2 to restart the program.
Find GetSystemTime again, click it, and press F2 to disable the breakpoint.
Now double-click it. You should now be looking at the actual code of the program near the call to GetSystemTime. What we want to do now is look for a CMP or TEST statement, followed by a CONDITIONAL jump, such as JE or JG. The jump is there to either display a dialog and exit (if it expired), or give you access (if it hasn’t expired yet).
Not all trial programs are the same, so I can’t tell you exactly what it will be like. Set a breakpoint on the jump (F2) and run the program again. If it still pauses before displaying a message or exiting, we're almost done! (If not, you'll need to look for another conditional jump.)
The program should now be paused, and the conditional jump should be highlighted. Double-click it so you can modify it. Make it the opposite of whatever it is (change JE to JNE, JG to JL, etcetera...), then click the "Assemble" button.
Press F9 to run the program again. Tada! Your program should work now.
Right-click the code again and select "Copy to executable" -> "All modifications", then choose "Copy all".
A new window should appear. Right-click it and choose "Save file" to save the program. Congratulations!
The End
i'm still investigating on the other type...
email me if in doubt
ps thank this guy called FreakWolfe, he gave the guide lines.