confused

how do i get my computer to see my other hard drive recently installed, it see’s it in the BIOS and also in the disk management option, but in there it is in black and says that it is unallocated and i can not format from there either. so is there another way for the computer to pick it up would it work if i have the xp disk and just format it that way would it see it then after that is all done…well if there is a solution out there anyone would do and i thankyou in advance.