Windows XP is on the C drive.
want to install Windows 7 on d drive,
- will it erase Windows XP?
- will it cry to be on C drive?
- it will happily accept Windows XP on c drive?
Yes this is possible - no it won't erase XP.
1) Boot from your Windows 7 installation disc.
2) Click install now.
3) Select drive D (make sure it's the right one - look at the size if you aren't sure)
4) Finish installing.
5) Restart to see a boot selection screen. You have the choice to boot to Windows 7 or to 'An earlier version of Windows' i.e. XP.