Your WinXP partition is probably NTFS. It is dangerous to write to it.
A fat32 Winxp partition works but you can't revert them. Most people
use a fat32 transfer partition that either OS can read and write.

I use WinXP's boot.ini file to dual boot (FC4 in this case):

[boot loader]
timeout=20
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOW S
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Micro soft Windows XP Professional" /noexecute=optin /fastdetect
c:\linux.bin="Linux"

Don't install the booting of *nix to the MBR but to the boot partition.
This order makes WinXP the default. The dd command is used.
http://www.geocities.com/epark/linux...w2k-HOWTO.html