I'm not sure if I understand the question completely, but you should restart your computer when you install anything. It makes the installation take effect and your game should prompt you to do so.
The game flashes?! I'm sorry but I've never had that happen to me. Try restarting your computer, or reinstalling the game and installing it again.
It may not be your game but your computer. Try to delete any of the old movies or games on your computer and that should speed things up a bit. However, if the game itself is slow, try restarting your computer or editing the game startup files. IF you dont know what your doing, i highly suggest you not modify game files.
When it's time to game!
You might be able to download them to the Computer, but that it not the same as installing them. Only PC versions of a game can be installed on a computer.
No. Installing and playing games on a computer only slows it down while you are playing them.
Not if it is properly uninstalled
U can try emailing it to yourself, or putting it on a flashdrive and installing it on the new computer.
by restarting your game
Probably not enough memory - try installing more memory.
Make sure you have all the requirements for the game before installing.
No, you download them straight from the PSN using the PSP.
put the CD in and install the game.