USB Pendrive letters assigning problem

[Tomaszek]

Hi,
I had a serious problem with my USB pendrive. The problem pops up out of nowhere and I had no idea what could cause it.
I had a C: hard drive and D: DVD drive, so when I stick my USB pendrive it appears normally as E: Now when I remove the drive and reconnect it (put again into USB) it is assigned as F: - when I repeat unplug/plug it is G: etc. When it finally comes to Z: no more letters are assigned. I can go to drive management console and manually assigne the letter, but after this during unplug/plug letters iteration happens again. More than that if letters assigning stops at for example M: in drive management console I can't assign to it letter which were already used. There are simply no letters in combo box. It looks like after the unpluging of drive the system is not releasing once allocated letter. Please help - any ideas are welcome.

I'm running WinXPSP2 no HP Pavilion DV1000 notebook. Problem occurs on various pendrives so it is not the problem with it.

Oh, one more - after restart OS keeps assigning continous letters only this time in drive management console I can manually assign it to E: or other letters which are previously unavaliable.

Thank you in advance.