Find out what MOBO you have
Upgrade to 2.71 ofw,since you don't have the games needed for the other downgraders.
Use generic downgrader for TA-82 MOBO's
For TA-082 you can use generic or
Easy 2.71 TA-082 Downgrader
Here are the links
Once you have downgraded to 1.5,use this tut. to get you to 3.90m33
2.80 downgrader cannot be used on TA-082 MOBO's
QUOTE(THE PSP MUST NOT HAVE A TA-082 BOARD)
If you have a TA-82 mobo you can upgrade & use the 2.80 downgrader.