Hi,I am using a Dell inspiron 1520, which recently was formatted. It originally had Vista installed, and after formatted they installed it W 7 ultimate, but when i try to install some applications it gives me a screen saying this: "internal error: Failed to expand constant "userappdata". Any solutions to this. Thanks in advance.

Web pages seem to suggest your system is somehow damaged either by malware or some other error. Some say the solution is to take the W7 DVD and install it as a clean install and not an upgrade. You may not like that if you would loose programs and data. Might try to use anti-malware programs. Start by using microsoft security essentials program and see what shows up. Playing to the angels Les Paul (1915-2009)

This was a clean install and it was just done, i don´t think we have any malware.

you could try putting in the dvd, and running a repair of the win7 installation, or failing that do a complete reinstal. i hate computers! but cant help myself....

If you know the system is OK and you are trying to load on applications that may not be Windows 7 capable then you may have to try other options. Might try compatibility mode on installer program and the actual program to run. It seems to be saying that ntfs permissions or registry issue is preventing app access to some area to write a file. Only a wild guess. Is this all applications? What is the ones doing this? Might end up reloading the OS and being careful on adding any non-supported drivers. ( I kind of think that would be very unlikely that a driver installed could cause this) Playing to the angels Les Paul (1915-2009)