This is a problem that has plagued me for some time. The problem generally occurs on the 3 Litre ACER L460 series desktop with the Windows XP Pro downgrade.
The symptoms may include the following:
1. Cannot run setup program from a CD.
2. Cannot run setup program after download.
3. Program hangs on initial start.
Thanks to some friends at TSH, we have determined that the ACER Empowering Technologies elock and LANscope Agent services interfere with the installation of some applications. If you run task manager, you will see lock.exe and lockkm.exe processes running. Terminating these services allowed the programs to load properly.
The solution we applied was to uninstall these programs from the Control Panel.