[Midian]

the drive is going to be different for alot of people.
by drive, i mean the drive letter your psp gets when it plugged in (for example, when i plug in my psp and open my computer, my psp is labeled as "Removable Disk J" so i use the drive letter J)

so it looks like this:
C:\Documents and Settings\Midian> cd C:\msinst
C:\msinst> msinst J msipl.bin
and so on and so forth.

just type that in and replace J with your drive letter. make sure you use a capital letter. (no=j yes=J)