I recently upgraded my 2 year old 260GTX Core 216 to a new EVGA 560ti.
I installed the old card in my brother's PC since he was still running integrated graphics; the system managed to post and boot into windows the first time around, but after that it constantly failed to finish booting (Windows did start loading, but the system re-POSTed before the start screen was reached) or turned off while it was in use.
Do any of you have an idea as to what this was caused by? My brother was running the latest EVGA drivers for the card and a fully-patched version of Windows Vista Ultimate x64.
Here's my brother's hardware configuration, for reference:
Your brother's hardware configuration isn't showing in your thread, you may want to edit that. But I digress, from the sounds of it, it's a PSU issue. If it's an older computer that wasn't built with a PSU that could supply enough power on the 12v rails for a modern GPU, you would definitely be experiencing this problem. Most commercially built PC's (PC's from Wal-Mart or any other major retail store ) tend have weak PSU's, too. Also, the wattage may be low. I believe the suggested wattage on the PSU for a GTX 260 is 450 watts if I'm correct. If his PSU has a lower wattage it won't be able to power the GPU either; effectively shutting down the PC.