hd drive assignment

I have a XP sp3 system and my usual drive assignment is :

C: hd1 / D: dvd1 / E: dvd2 / F: hd2 / G: hd3 / H: hd4.

There is no installation or removal of hard drive recently and suddenly the assignment changed to :

C: hd1 / D: hd2 / E: hd3 / F: dvd1 / G: dvd2 / H: hd4.

This creates a lot of problems for shortcuts, programs, folders... as the drive reference is mixed up. Is there anyway to control the assignment of hd drive so that I can have my usual hd assignment back ? Thanks .