What OS are you gonna use?
The 8800GTX is G92 (as far as i am aware) so your home dry with that, just make sure your PSU (Power Supply Unit) is up for it, check that they are SLi/Crossfire certified, but also the rail amps are up for it. The rail is the cable running from the PSU to the graphics card. What PSU you getting and we can have a quick look for you.
You need floppy drive for XP 32-bit if they driver hasnt been slipstreamed in. I always put floppys in all the PC's i build, to get the RAID driver its best to download it from the motherboards website. If they come down zipped or rarred, unzip and unrar them and copy them to a blank floppy disk.
The following guide is for XP Pro SP2, its a general guide, your motherboard and setting may change but you get the general idea.
Install all the hardware, connect all the cables and power it up, go straight into the BIOS and with the manual at hand, select and enable RAID in the BIOS. save and exit, the PC will reboot, now closely atch the text that appears, if you see somthing like " press CTRL + F/I/Y to select RAID" press those keys, the last letter may change but you get the general idea.
If you have power to the CD/DVD drive its always good to put the OS disc in now.
In there you build the RAID, its all done by keystroke on your keyboard by pressing 1,2,3 or 4(any i have done is by that) then select the hard drives that you want to use as a RAID 0 or stripe RAID, select the cache to 128KB and enable write-thru. save and exit, the PC will restart, go back into the BIOS again and select the boot order for CD/DVD drive first, hard drive 2nd, floppy 3rd, save and exit, the PC will restart again, let it pass all the logos and pass the RAID screen, then the CD/DVD will start to spin and you should see "press any key to boot from CD", hit enter and get ready to press F6, read the white wrting at the bottom of the screen when it says "Press F6 for RAID or SCSI" press it, and let it continue, pop in your floppy and wait for the on screen instructions, a message may appear that no hard drives were found and to specify a drive by pressing S, hit S and then it will sayto insert a floppy and press enter, do that and it will search the floppy for drivers. find the one for your motherbaord if more than one is listed, normally X86 XP would do the trick, X64 is for a 64 bit OS. press enter and it will install the drivers for the RAID so XP can see the SATA (Serial ATA) hard drives in a RAID (RAID = Reduntant Array of Indepentant Discs* makes the PC think there is one hard drive when you actually have more than one) from there then you can partition off a section of you hard drive for windows and make a C and a D drive, but totally up to you, to install theOS select the drive (always best to use C) and press enter, quick format it, the setup files will copy over and the PC will restart....
*WARNING*!!!!
apon restart the message will appear to press any key to boot from CD.....DO NOT PRESS ANYTHING....let it off...... the windows XP logo will appear with the blue bar going left to right and the install will start.... going on your PC specs it should install in under 8 mins. Enter in your CD key for windows (Tech power up will always assume you have a legit version *cough*) enter in your time and date, location, network setting, leave it as workgroup and it will finsih the install, the PC should restart again.... don not press anything, and will show the XP setup for your name, wnter in your name, save, and it should continue to the desktop, take out the CD and floppy, install the drivers from the CD, the PC will restart again, then install your internet securities, AVG/Bitdefender/Kaspersky...anything but Norton or Symantec....... the PC will restart after internet securities install, now wuld be a good time to change the boot sequence to: 1: RAID hard drive, 2: CD/DVD 3:Floppy, save and exit... but go through the manua for other settings like CPU temps and CPU Fan speeds controls. boot up and get your internet securities up to date and get your XP up to date...but do not take down ANY microsoft hardware updates...they are crap, only use manufacuter ones..... also you might need .Net 2.0 installed before your graphics card is installed, you can get them from microsoft.......
the above is from memory..... i hope i havent missed anythng..... but read your manual for the motherbaord and ask us for help if you need it.........
right now my fingers are wore down to stumps!!!!! hahahhahah