How to H4x0r

OK, since you can just hack Castlevania: Aria of Sorrow to your heart's content from Visual Boy Advance, a separate hex editor is not required. Yay! While playing the game, go to the Tools Menu, then to Memory viewer. You'll want to be in 8-bit mode or 16-bit mode. If you're in 16-bit mode, you'll have to flip values around when you enter them if they take up more than 1 offset. But I still like using 16-bit, since that's what I'm used to. Anyway, type the address you want to go to in the box in the upper-right corner, then click Go, and you'll magically be transported there. Hurray. Now you enter the value you want to change, and voila! For example, if you want to edit your character's Level, type 02013279 in the box and click go. You can confirm your address by looking in the box at the lower-right. Let's say you want your level to be 7 for some reason. Replace what is in that offset with 07, and you've done it!

There's really only 1 way to hack in Castlevania: Aria of Sorrow.  It's as simple as putting in a number.  You use this one for altering the character's statistics (HP, MP, Level, etc.), money, and number of items and souls.  For example, if you want to have 9 Hammers, you would go to the offset in the code which controls the number of Hammers, and change it to 9.  Not tough.  There is a catch though.  Save states are saved in hexadecimal (base 16), which is not the normal way of counting.  Normally the first number to the left of the decimal is the 1s column (note that 1 is 10^0), the one to the left of that is the 10s column (note that 10 is 10^1), the one to the left of that is the 100s column (note that 100 is 10^2), and the one to the left of that is the 1000s column (note that 1000 is 10^3).  However, in hexadecimal the first column to the left of he decimal is the 1s column (note that 1 is 16^0), the one to the left of that is the 16s column (note that 16 is 16^1), the one to the left of that is the 256s column (note that 256 is 16^2), and the one to the left of that is the 4096 column (note that 4096 is 16^3).  So in order to make 0 through 15 all fit into the 1s column they use letters in addition to numbers.  A 0 in decimal (regular numbers) is a 0 in hexadecimal, a 1 is a 1, a 2 is a 2... a 9 is a 9, but a 10 in decimal is an A in hexadecimal, an 11 is a B, a 12 is a C, a 13 is a D, a 14 is an E, and a 15 is a F.   Keep that in mind when entering numbers.  Just as a quick reference, 99 in decimal is 63 in hexadecimal (9*10^1+9*10^0=6*16^1+3*16^0). If this is too complicated, your computer probably came installed with a little calculator that can do Hex-Decimal conversions for you.