Ok, this is a special package which you can only find here. Its clean off of all other unnecessary files and only left with the files for PSP Slim V3.71M33. I had prepared everything you need here. V3.81.1 included the support for multi disc PSX which is implemented in 3.71M33-4 firmware which you will find details in previous post.
Because I had "patched" the V3.81 to V3.81.1 inside here, so there is no need to download 1 full install and 1 update. This is the full 1 step to V3.81.1 install. I had also ripped out the PDF for those who think they can handle without the doc. However, I had uploaded them as a different file in case you want them anyway.
1. To install, extract all the content of the main zip to your PSP MS main directory. Yes, all the directories are build properly.
2. Start your XMB (which is the lbue screen menu by sony) and run the iRShell application.
3. Click on the first icon which is the Directory View.
4. Click .. to go up to the main directory if you are not there already. Find /IRShell//PATCH/3.71.
5. Click X on the file btcnfpatch.prx and run it. This will patch your 3.71 firmware to autorun IRShell.
6. We are not done. Many people did not know this and have problem running ISO/CSO. Now go to the icon that says iR Shell Configurator. Its the middle one in the last row. Run it.
7. Find UMD Mode. This is the 3 line from the top. Change this to M33 NoUMD Mode. If not, you will always get the no disc inserted error when you run a ISO/CSO.
7. Thats all you need to do. I may want to show you some skins and stuff, but thats in another post later. Other stuffs, RTFM.
Here are the files.
Main files :