I want to put in a hard drive for my PS2 but it wont read discs except PS1 or purple I think but want to know if I put in a hard drive will I still be able to play games on it and will I be able to install Hard drive?
If you have a weak laser, my recommendation is to get a modchip installed that will boot off a memory card (ie Dev 0 mode). Then, you can run software that will let you do just about everything except play PSOne games from the hard drive.
I'd recommend either Team Modders or NorCal Mods for a chip + install. Should be in the range of $60 plus shipping. Set up properly and running uLaunchELF, you can do just about everything and not need a working laser. You can't play PSOne games and about 10% of PS2 games, but that pales in comparison to what you get with the modchip.