installing windows 7 on a dual boot with xp confusion

hi all , i need some help regarding installing windows 7 on dual boot machine with xp installed first..

first of all i formatted my laptop yesterday and i did installed windows7 a fresh install as a single boot machine only . when i tried to format my hdd to create 2 separate partition (c,d) a pop up windows appears and it told me that windows 7 need to create 100 mb partition for the windows system file in order for windows7 to function properly . so i accepted...

now i am planing to install windows 7 along with xp on a dual boot machine on my other pc , so i know that i will install xp first on drive c , and win7 on drive d , in this case drive will be formatted by windows xp during the previously created partition by xp , after finishing installing xp i will boot win7 disc and i will installed on drive d ..

the question is do i have to format the drive d again by windows 7 by clicking on advance button at the beginning of the installation , or because i did previously formatted the drive by xp so it is no longer necessary to formated by win7 ?...and if i don't have to format my drive by windows7 , what will happens to the 100mb partition for the win7 system files..

i am asking this because i got confusion by the pop up windows that appears when i installed win7 that asking for the reservation of 100mb for windows7 in order to function properly....

i know it is little confusing , and thank you all for the help..

hi and thanks for help , i did installed as you told , and by the way when i did format the second partition again by windows7 installation disk it did not ask me to create 100mb for the system files , so as i noticed when you are installing win7 on a single boot machine and you try to repartition your hdd , in this case win7 will ask you to reserve 100mb , but in case if you installed on a dual boot with xp installed first , then it will not ask even if you delete and create the second partition by win7 installation disk

again thanks for the help , and have a nice day...

First Install windows XP in c:
Then you can install windows 7 in the same drive. Using the "new installation" option.
So it is not required to format d: