[ex] Shorty,
Sounds like you may have a system file problem on that machine. Couple things to check.
One make sure you have a C:\Documents and Settings\user\local settings\temp. If you dont then create one.
Also its possible you may have to be logged in as the administrator of that machine.
If these things still dont work check your system files.
System File Checker - This is one of the most useful tools built into windows XP, it can be called into operation from the the command prompt (Start - Programs - Accessories - Command Prompt/Dos Prompt ). Once you have the command prompt box open type sfc/scannow and hit enter. It will often require you to insert a operating system disk to make any repairs to the file system that it detects might be corrupt.
Give these a try, then retry to download the Install 1.9.exe from
www.winmxgroup.com then make sure its 1.3MB in size when done downloading then retry the installation.