There are 12 months in a year, thus 12 possible backgrounds for the PSP. You MUST rename the bitmaps you download to XX.BMP (XX represents numeric two digit month)

Examples:

01.BMP - January
02.BMP - February
03.BMP - March
04.BMP - April
05.BMP - May
06.BMP - June
07.BMP - July
08.BMP - August
09.BMP - September
10.BMP - October
11.BMP - November
12.BMP - December

Remember the following rules when using a custom background - the image must be:

24-bit Bitmap (BMP)
less than or equals 150KB in size
less than or equals300×170 resolution

Main Tutorial :
1. First create a USB connection between your PSP and PC.
2. Extract PSPersonalize_v1a-kxploit.zip(google it ITS AVAILIABLE EVERYWHERE YOU KNOW IT) to your memory stick under \PSP\GAME - this will create two directories, so you’ll end up with:
1. PSP\GAME\PSPersonalize%
2. PSP\GAME\PSPersonalize
3. Rename your BMP’s respectively
4. Copy the BMP’s to the root directory of your memory stick(meaning the very first window you see on the stick not in any subfolders).If Windows recognizes your PSP as drive letter i: then copy the bitmap(s) to i:\

1.Browse to the Game menu on your PSP
2.Select PSPersonalize - disregard any “Corrupted Data” - it’s nothing
3.Boot PSPersonalize
4.It will automatically detect the BMP’s in the root directory. Press “O” to confirm the background change or press “X” to cancel
5.You’ll end up at a “finished…” screen. Press “Home” and return to the PSP menu
6.You should see your background, depending which month you selected. If you don’t try rebooting the PSP