So what I did till now:
1. I tested with 2nd PSU ... PC restarts.
2. I removed 3 sticks of RAMs total 32 GB could not remove the last one as it is stuck below my huge cpu cooler... PC restarts.
3. Tried to installed Linux on different SATA HDD hard drive ... PC restarts.
4.Tried to install WIN XP 3 on sata HDD it worked NO restarts.
5. Installed WIN 7 32 bit with new install CD on sata HDD it worked, NO restarts. So I formatted my SSD with NON-quick option and installed writing software to wipe the rewrittable dvd to burn new image on WIN 7 64bit with 2X Speed with "verify after write "option selected.
6.
Installed newly burned WIN 7 64 bit with same rewritable DVD on SSD it worked. NO restarts.
So though my PC with win 7 64bit is running well for last 7 -8 hours. with one stick of ram instead of 4. It is still not known why it did not work well before...?
as above it should not have been restarted when I was installing Linux with new install CD on separate SATA HDD because on the same HDD later WIN XP installation worked...
Though I have done two changes:-
1. WIPE SSD fully, not quick....
2. Rewrite WIN 7 install media again with rewritable dvd with 2X speed.
It is still not known why it did restart when I was installing Linux on same SATA HDD where WIN XP installation worked...?
I gave entire whole yesterday troubleshooting this things just to know that it just worked well automatically without resolving any particular issue.
Thanks.