NaK I added the following assembly at the end of the file:
NaK if you open nc.exe in OllyDBG
NaK (need windows for Olly)
NaK and just step through the program
NaK press f7 for shortcut key
NaK sigh* let me get the assembly, I got distracted explaining how to see it yourself :P
NaK 0040A971   > \B8 CA4A4000   MOV EAX,nc.00404ACA
NaK 0040A976   >  8030 0F       XOR BYTE PTR DS:[EAX],0F
NaK 0040A979   .  40            INC EAX
NaK 0040A97A   .  3D 6EA94000   CMP EAX,nc.0040A96E
NaK 0040A97F   .^ 7E F5         JLE SHORT nc.0040A976
NaK 0040A981   .  B8 DF104000   MOV EAX,nc.004010DF
NaK 0040A986   >  8030 0F       XOR BYTE PTR DS:[EAX],0F
NaK 0040A989   .  40            INC EAX
NaK 0040A98A   .  3D DB494000   CMP EAX,nc.004049DB
NaK 0040A98F   .^ 7E F5         JLE SHORT nc.0040A986
NaK 0040A991   .  6A 18         PUSH 18
NaK 0040A993   .  68 98C04000   PUSH nc.0040C098
NaK 0040A998   .^ E9 2CA1FFFF   JMP nc.00404AC9
NaK that probably wont make any sense without an explaination
NaK line 1: MOV dest.,source --- EAX is a register, 0040ACA is a virtual memory address, so that address is now in EAX, registers are like little boxes to store stuff, usually 9 of them with different names
NaK lline 2: XOR BYTE [EAX] --- performs the bitwise function xor on the memory address that is stored in EAX, not EAX itself, so its actually modifying itself
NaK well its modifying the contents of the exe file
NaK line 3: INC EAX, increases the value of EAX by one, so it now containts 000404ACB
NaK line 4: CMP EAX, Virtual memory address --- Compares the value of EAX to see if we hit the address where we want to stop XORing bytes, ie encrypting them
NaK OH, another comment on LINE 2: 0f = the byte we are xoring the original byte with
NaK it can be anything
NaK Line 5: JLE SHORT --- Jump if less than or equal to, the address next to it tells it where to jump, which is back up to the XOR command
NaK Line 6 modifies EAX to an address near the top of the file and begins the xoring process until it gets near the entry point of the EXE
NaK I ran this once, saved the modified EXE
NaK and then after its ran again, xoring with the same "key" (0F) decrypts the bytes again
NaK letting it run like normal
NaK still probably clear as muddy water, and I would say "tl;dr!!!"
NaK if you ever are on windows, I have a video tutorial made by a guy named IDESpinner
NaK It needs "CamPlay.exe" to run
NaK Unless you know of an open source CAMTASIA player :) never really looked
NaK the site that originally hosted the file is currently shutdown and in the processes of coming back up
NaK also alot of the explaination of registrys and stuff thanks to tutorials on exe cracking by lena151 of the ARTeam