hard disk disappears at each boot!

Hi all,
After reinstalling succesfully XP on my PC with lots of problems due to the amount of viruses out there, my computer do not “detect” the second disk:
. it is recognized at the BIOS
. it has been partitioned and formated, even I moved over there the TEMP folder
. the partition was “activated”
Every time I boot my pc the disk “disappears” (from explorer, from XP’s disk management) but after running the “new hardware wizard” it “re-appears” and works just “fine”.
Please your help will be appreciated,