I cant install sis apps on my nokia 6220c. It says expired or invalid certificate. Pls help

In what way? Is it that it's not accepting the application or does it accept it & not opening it? Just try and install different version of the app, your phone may not have the security certificate for the app & this may be solved if you have a computer system with bluetooth dongle & bluesoleil software on it, with this you can access the phone memories on the system directly on the computer, just copy & paste the application into the memory if you already have the app on your system, but if you dont, you will have to find a way of getting it to the computer memory, for the latter your phone might have been infected with virus, try formating the memory or restoring factory setting if you know your security code! If none of these work, go & flash the phone, but there are risks. Still have problem? I am sorry you have to get yourself a new phone if you know you need an application.

Here's wat my friend said he did 2 solve d prob.
'D stuff is dat , in order 2 signapps easily without cert error or expired cert, u av 2 hack ur fone with HelloX or sum oda type. I got mine hackd on nairaland by a member'.
So please can any1 help me hack or soil my nokia 6220c?