For Simple Invoices to work on your server/pc your php.ini file needs to have a few settings

gd
GD Support 	enabled
GD Version 	2.0 or higher

;;;;;;;;;;;;;;;;;;;
; Resource Limits ;
;;;;;;;;;;;;;;;;;;;

max_execution_time = 90     ; Maximum execution time of each script, in seconds
max_input_time = 60 ; Maximum amount of time each script may spend parsing request data
memory_limit = 24M      ; Maximum amount of memory a script may consume (8MB)             

Beta release - in the Beta 1 release of Simple Invoices PHP 5.2 is required as well as PDO and PDO_Mysql

add php_info() settings to