Hey guys, I got a Asus P6X58D Premium from a friend; however, I didn't get all 9 standoffs that are needed for the mobo. The Antec 1200 case that I got came with 9 female standoffs, but I can only screw 7 of them in. This seems to hold the motherboard fine, so would I need to screw the other 2 standoffs in also?
If your planning a permanent system, with an aftermarket CPU/HSF - you're not going to be removing the board and components every week, I would use at least 8. Those screws and stand-offs will be supporting the entire weight of all the components you plan to install to the board - the more you have, the better distribution of stress on the board you'll have.
Typically, the standoffs are for suppor and to ground the motherboard so it won't short out. I would recommend all the standoffs being installed to 1) help prevent shortage & 2) motherboard support, as treefrog06 stated.
Be careful you don't place standoffs where there is no mount point on the motherboard though. I had one system come in that someone had built and he couldn't get the OS to install and the hard drive was behaving very oddly. After much troubleshooting we dismantled everything to test individual components and we found one standoff had been installed right under the ATA headers and it was shorting out the connections. Removed that standoff and the system started working finally with no issues.