Sony Vaio: Downgrade Vista > XP

Hi, I sure could use some advice here. I'm an old desktop guy who's been building boxes since the 8088 days. The thing is, I haven't done any substantial laptop work in several years.
The problem is when I attempt to downgrade from Vista to XP Home on my friend's wife's new Sony Vaio. I don't have the model number handy but it has the C2D T5450 1.66 Ghz. CPU and the system shows a 160 GB hard drive. There's also a "memory stick" drive that comes up but I'm guessing that's the SD card reader.(?)
Anyway, I can't find any way to install XP on this system or even reformat the hard drive. When I try to run "setup" from the XP CD with Vista booted, "Setup Windows XP" is greyed out on the menu. When I make the CD bootable and try to install it that way, it goes through the motions of copying the files then tells me that installation can't continue because it can't find a hard drive installed on the system!(?) I can't even find a way to access anythig resembling a CMOS on this thing. This is not nearly as straightforward as the same task on a desktop.
I'm hoping someone around here with a lot more notebook knowledge than I could give me a hand. I'm totally at a loss here. I'm sure this is some "notebook newb" issue for my part, but I'd be forever grateful for any advice I could get here.
TIA,
MC

Ya know, you're the second person to warn me about the lack of drivers for these new Vaio systems for XP. On third though, I'm just going to tell her she's stuck with Vista or pay someone else to do it. I'm not messing with it.
Thanks for the help!

First go to sony's site make sure you have all the drivers first, the biggest problem with a downgrade is the SATA drivers, which are not native to XP, and if you don't slipstream them into your install or else get a seperate driver install disk to prep your boot, then you will need to manually download them and manually function key add them to your boot/install.

Also you need to do two things, first grab all those drivers etc, and get them ready in the needed format. Does it have an intergrated optical drive could tell it it was external or not (makes it easier than installing from USB or network)?

Second, you need to find a way to get into that BIOS so you can change the boot order. If you can't get into it normally you can do the very VERY dirty job of formating the disk externally this is an absolut last resort.

Most importantly check the sony sites (from around the world sometimes drivers are found at the Dutch or Germany sites either due to their laws or the usual demands of their customers). I only found the materials and software for my Sony HD camcorder on a foreign site site (not the ones I listed so as to not compromise that source).

Anywhoo, most important thing I found when rolling back from Vista is the online forums that specialize in the product.

Also if Sony has a driver disk to aid the rollback it may be worth it for you and the owner to spend the $10-15 S&H charge to get one, pester them a bit if they give you a hassle, if it's Vista Business or Ultimate then they likely already have alot of these requests like the rest of the companies that offer the 'downgrade'.

PS, would probably help knowing the model number, but likely can't give you anymore info even if I had it. But provide it to the next forum you ask to help them because likely in a dedicated forum someone has done the same thing with the same laptop.

first can use the diskwizard then format hardisk &restart ur system,to install ur windows xp. this is rjs from dmm(atp) ap.