Cannot run exe across network or internet

I cannot run an exe file across my network or the internet on one of my
computers. All run Windows XP and all other computers can. The only
difference is the one in question runs XP media center.
The reason this is a problem is some sites run program that downloads and
installs the product (i.e. I-News and Logitech QuickC am software).
I have stopped all startup programs and all non Microsoft services in
msconfig and uninstalled several programs that I thought might interfere.
I think it might be a registry value but do not know where to look. Any help
would be appreciated.

Sam Roe