How to change the content of a file w/o changing it's size?

[SandsOfTime]

No idea where this should go so i posted it here.
My uncle recently asked me to modify a file for him however the catch is, it must be of the same size of the original despite changing it's contents.
How do i go about doing this ?
a Simple tut/ URL will be very much appreciated.

[KFSPC8]

what kind of modification do u wnt to do on the file? a .txt file?
keeping it the original size sounds sneaky

[guyz92]

Possible Hex editing.

[SandsOfTime]

It's an .Exe file, He asked me to change some letters inside so it'll read another file instead of the intended one.
I've tried using EditPlus however all i get are some squares and chinese characters.

When i try to view em in hex using Edit plus, i'm unable to edit them o.o

Edit: When i change it from a .exe to a .txt to edit it and back to an .exe to use it.
The icon changes from a picture to the standard. exe picture. Does this affect anything?

[wizme]

you cant change a .exe to a .txt and hope it will become plain text. exe is a binary.

[SandsOfTime]

So i'll have to open it with a programme right? I've tried edit plus X: but i get squares, have tried various encoding options but still squares /:

[wizme]

Depending on the binary, most of them cannot be reversed engineered to see the source. You can try to use cheat engine to change the exe.

P.S. You cant change the size to a smaller size than the original but you can increase the size of a file by padding it.

[SandsOfTime]

Oh alright, any cheat engine will do?
What's padding? do you have a guide for it? thanks><

[wizme]

Why dont you upload the exe and tell us what you wish to do
We'll see if we can help you

[SandsOfTime]

The File can be downloaded from here:
http://www.mediafire.com/?054eykf2hc7maxd

It's an exe file though, how do i post a virus scan? incase you guys want it.
My uncle wants me to change the G e n P a r a inside the file to a P e n P a r a.

Thanks.