Help needed

[blazer1504]

I'm having little trouble with my install script and I'm wishing that maybe some of you guys could help me with this:

Okay, what I'm trying to do here is to detect winamp2 to $1 and Winamp3 to $2

ReadRegStr $1 HKLM \
"Software\Microsoft\Windows\CurrentVersion\Uninstall\Winamp" \
"UninstallString"

ReadRegStr $2 HKLM \
"Software\Microsoft\Windows\CurrentVersion\Uninstall\Winamp3" \
"UninstallString"

These sets wa2 (if exists) to $1 & wa3 (if exists) to $2, right.
because we get the path in file format (...\winamp(3)\uninstall.exe) I need to get that file stripped, and here's where I have problems.

With what function I could erase the letter from both, $1 & $2, one by one until the last letter would be different ?

Or with what function, I could erase letter from both , $1 & $2, one by one until the first ' \ ' mark comes ?