ur data is in the third partition ?
boot from ur winxp cd
format the primary partition and install winxp on that
after ur done and u boot into ur os format the second drive with the other windows
all ur data will be safe since its on the third partition
if after all this its giving u a dual boot option ( which it shouldnt )
find ur boot.ini file in c:\ ( root drive )
and open it in notepad
and make sure it reads like this
Code:
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect
have fun