OK, TBH I don't know what you're doing wrong, but I know how to do it right! (BTW, yeah, I remember you, from the good old days. )

I'll write a short tutorial for you, assuming you know how to do stuff like extract, copy files to the PSP, etc.

Do this stuff on your fat PSP -

1. Backup everything important on your 1GB MS. (VERY IMPORTANT)
2. Download this, and copy the CSO* file into the ISO folder on your MS. (If there isn't one, make one next to the PSP folder and put the CSO into it.)
3. Grab the 1.50, 3.40, 3.71 and 3.80 official upgrades. Rename them to 150.PBP, 340.PBP, 371.PBP and 380.PBP respectively. Put them next to the PSP folder. (psp-hacks.com has them if this site doesn't.
4. In the XMB, press SELECT and change UMD Mode to "Sony NP9660".
5. Start UPMS Installer from the Game menu.
6. When it asks you, select the option to install the mod/plugin/whatever. This will allow IPL writing, which is required.
7. Your PSP will restart. Go back into UPMS Installer, and as you've installed the mod, you may press X to proceed.
8. On Step 1, install Sleep Fix Multi-IPL.
9. On Step 2, select the option to create Pandora battery.
10. On Step 3, you may choose between the fast version or slow version. The slower version has "utilities", but the fast version has everything you'll need.
11. Then exit the installer. Put the 1Gb MS into the PSP Slim, then the battery from the Phat into the Slim.
12. Go into Despertar Cementario (DC, also known as Universal Unbricker), and select it. Select the option to install 3.80 M33, and let it complete.
13. Da daaaa! Your PSP Slim is now on 3.80 M33! You may upgrade it to 3.90 M33 as you wish!

So, there ya go. Try that out, it should work. If it doesn't, tell us how far you got.

BTW, are you staying?
*This CSO is legal - it's homebrew-made.

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