Concur, no problems. A small twist. If your motherboard gives you the option of selecting Boot drive (Mine is F12 while booting). You can eliminate the software boot manager. ie if you already have XP on one drive. Disconnect that drive, leaving (or connect) the 2nd HDD and install Win 7. Then reconnect XP drive and select which operating system you want to boot to.
If a new installation of both operating systems, then just connect one drive and install operating system. DOES NOT matter in which order. Once you have that operating system up and running, disconnect HDD and connect 2nd HDD and install the 2nd operating system. Once installed, reconnect the first HDD.
While most do not experience a problem with using a software boot manager there have been some isolated cases that a problem on one drive has messed up the 2nd drive.
Anyway either method works - just a alternative method to achieve the same goal.
WOW - I must be a slow typest, 2 more post between mine and stubham1401
You will not have the possible problems noted in scotteq's link. When booting Win 7 the XP HDD will be fully visible and you can read/write to it and visa versa when booting XP. Note which ever operating system you boot to, THAT WILL be your C drive. If boot drives are partioned so that you have a C, D, E, F. Operating system will be C. The other drive letters may also change, You just need to be aware of that. I have no proble, I am using drive letters C thru I HDDs), Just gave each drive a discriptive name, ie Vista, Win7, Video, MyData (for Small files), Backup.