Perple_X programs require a larger amount of memory than is usually 
allocated on personal computers. WHen this is the case, the programs 
generally will not start and you may or may not recieve messages such as: 

"System cannot execute the specified program"
"Paging file is too small for this operation to complete"

In this case increase the "System page file" (aka "virtual memory")
size as follows:

Under Windows: -> My Computer -> Properties -> Advanced -> 
                  Peformance -> Advanced -> Virtual Memory -> Change

Increase the page file size (be sure to press the "Set" button to save
your changes), to at least 2 Gb and reboot the computer. If this does 
not work, first verify that the page file size has in fact been 
increased. If it has, try increasing the page file size to 4 Gb and 
reboot. If the programs still do not start, the problem probably lies
elsewhere.  

see also www.perplex.ethz.ch/faq/running_from_a_windows_console.txt