It will work. Get the xp boot cd and insert it. If it doesnt load click the settings thing when computer starts up (usually F11) and change boot order to cd. If you don't know how to do this you can always google it. BTW are you going to dual boot it with vista? If you want to you will need to partition your drive and then you can either manually change the boot order to check for other OS's or you can use a program like vista boot pro. I would dual boot if i were you though.
It won't work unless you know how to slipstream SATA drivers onto the XP CD.
Since XP does not recognize the native SATA drivers if you try to install XP, it will tell you that your Hard Drive is missing or damaged.
Use nLite to slipstream drivers onto the XP CD, it is freeware.
That is the only way to get XP on Dell Inspirion 1525.
Be really careful. You need to install the correct peripherals so XP will work. I just had a problem where I tried to install XP over Vista. When XP started, every USB port shut down, and the video card would only use basic functionality. Just a warning.