Hi! i've bought VMInvoice but i can't install it it tells me

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, This e-mail address is being protected from spambots. You need JavaScript enabled to view it and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

i've tried to install from folder but nothing

i've copied my joomla 2.5.6 website in another server but it tells me it cannot create the folder

how could i do?? i need to use the component i've buyed please help me!! thank you

Hello. Firstly, sorry for replying late. If there is "Internal server error", try enabling Joomla! error reporting to Maximum (in Site -> Global Configuration -> Server) to learn more about the error.
Most probably, for your second error and maybe first also, it is because of insufficient folder permissions in your Joomla! You can check it in Site -> System Information -> Directory Permissions. It should be all green. If not, connect to your site by FTP and set folders as writable.