patch it's called
http://unxutils.sourceforge.net/
or use winmerge or so.
dunno Some windows user can probably tell you more about it

oh good. thanks a lot...really appreciate it!

actually, could somebody help me with the cmd line to type in in order to merge the diff file? I have no idea what to type

decompress cvs in a directory;
put patch.exe from unxutils and the .diff into that dir
run:
patch -p0 <filename.diff
where filename is your patch

i tried that but when i entered that cmd line, nothing happened...it just went to the next line, but did nothing. Pressing enter only brings me to the next blank line

Sounds like something is wrong with the <filename.diff part that is causing it to get input from the console (keyboard) instead of the filename.diff file.

try:
patch -p0 -i filename.diff

thanks for your help. So all i need would be the patch.exe and the diff file?