Windows 7: Multiple hard disks question

I am getting ready to install windows 7 professional on my XP machine, I know I have to format the hard disk. If I have two hard drives and just copy everything from the drive I'm erasing to the other one and disconnect it during installation to make sure no data gets lost, will the second drive still work when I reconnect it after the install is finished? Both drives are IDE

If you disconnect other drive you will not have a dual boot machine, either leave drive connected and you will have the option of which win to start at bootup.
Or if for some reason you wish to unplug it and wish to make dual boot later use easybcd software to edit boot files, or you could use win 7 repair facility to repair boot files after but you will have to run this function 3 times to be sure of a complete repair

See Brinks tutorial on creating a dual boot system with XP -=> here

Sounds like you want to say goodbye to XP. Sure you can move your data onto the other drive and then disconnect it. Good idea, as sometimes a second data drive can confuse the installer.

Boot from the Windows 7 DVD and select Custom install and then Advanced Drive tools to delete all, create partition(s) as your wish, and then format before install.

Afterwards, plug the other data drive back in and it should be seen via explorer. If not, assign it a letter in Disk Management.