I have PC with installed Windows XP Professional SP2.

Once I bought 2 SATA Hard Drives to make RAID 0.
Unfortunately my MotherBoard do not support any RAID, so I had to use
RAID 0 which is available in Windows XP (it named as "striped volume" in Disk Management).

I successfully did all needed for this operations and in addition decide to
Move Windows Swap File to new partition on RAID to increase Virtual memory performance. I turn off swap file to all other partitions except that on RAID and set size of SWAP file to maximum (4Gb). After that Windows created 4Gb pagefile.sys on RAID partition as it might be expected.

BUT, to my amazement I find, that my Virtual memory is only 2Gb and there is pagefile.sys on partition there Windows is installed (not on RAID). And it have precisely 2Gb size, although virtual memory configuration options still display, that swap file is turned off for all partitions not on RAID and that Virtual memory size is 4Gb.

Does anyone know what the problem? Maybe Program RAID in Windows XP and SWAP files could not be placed on the same partition? Could anyone explain the situation?

A couple of things here.
Do you really need a RAID system ?
If you do it's best to use hardware instead of sotware RAID.
As your Mobo doesn't support RAID I'd go for a separate SATA RAID card.

Concerning the page file.
In relocating the page file, it must be on a 'basic' drive. Windows XP appears not to be willing to accept page files on 'dynamic' drives.
As RAID is dynamic (in software mode) it won't work.

Rather than setting a overly large pagefile you would be better off installing more physical RAM.
It's so much faster.
My laptop runs 2Gb RAM with minimal page file, about 300Mb for debugging, and runs like a dream.

Yes, I really need RAID, because I need a lot of Disk space (I download a lot from Internet) and as I am a Gamer, want to have faster Hard Drive (read from RAID 0 have double speed).

When I buy 2 HHD for RAID, I was sure, that my MB support SATA RAID... as most MBs at the moment. But that was mistake - it was rare exception for ASUS Brand, when there was SATA and there is no SATA RAID (although there is some "strange" RAID controller, which I cannot use for SATA). So I had a choice: go and buy SATA RAID controller or Have what I have. As I am a lazy man - I prefer the second and try with Windows Striped volume.

Thanks a lot for answer, it was useful.

P.S. I have 2Gbs of RAM either, but some times I run out of it (games are very wasteful to recourses, you know)... so... swap is on.

elrik, you don't need RAID for gaming.
Have a look at Western Digital Raptor drives.
They have a spindle speed of 10k so the seek time is minimum.
Apart from going for full server SAS drives these are the fastest you'll get.
Using Windoze to control your RAID will cause a slow down of the system.

Now as a gamer (and general speed freak) myself, you need to look at tweaking your system for max performance.
Turn off all unneeded services and trim the startup to bare minimums.
Also, of course, a serious graphics card/cards is a must.
I'm running a Geforce 7950 GTX with 512 Mb and I haven't found a game that doesn't run below 25 fps at 1920x1200 with all detail on max.
This is perfectly playable ;)