Intermittent wifi problem on netbook Sony Vaio VPCM120AB. Also, no WPS

A friend's netbook with Win7 Starter got a virus hard to remove, so it's time to format and reinstall everything. After reinstalling Win7 Starter 32-bit and properly validating it with the serial on the tag under the notebook (which is strangely different from the serial I stripped from the registry), updated everything, installed and validated Office with original S/N, installed a few other essentials (MSE, Chrome, Adobe Reader, drivers from Sony website (but NOT the bloatware programs), 7-zip, etc) and installed linux in dual boot. Connected normally to my home router and I didn't see any problems with connection dropping, but wouldn't connect to my friend's wifi using windows - which is strange, because it always used to connect to it with no problems and no other smartphone/pc has problems connecting to it. It would tell me "wrong password" as soon as I hit enter, seemingly without checking wifi's password. I had no problems connecting when booted to linux, though.
Then I brought it back home, reinstalled everything from the start, re-updated everything, etc. While in windows, the netbook disconnected once from my home's wifi and would show a "red X" over the network icon, which I assumed to be because I was updating drivers, installing stuff, etc, so I just rebooted and everything worked normally. But this time win7 still wouldn't connect to her network, despite linux would connect normally. After fiddling with her router a little, I did manage to connect to it by disabling WPS, but now the wifi connection keeps dropping for no apparent reason and the "red X" over the networking icon shows, and no wifi networks are shown.
To make matters even more strange, I plugged an external usb-to-wifi adapter and it would work normally even when I had the "red X" while using the internal wifi board, but (iirc) it still wouldn't work with the router when wps was enabled.
So, WPS wouldn't work at all and internal wifi would fail sometimes, which is solved by rebooting. Even while internal wifi was on "fail state", external wifi would work normally; not a hardware problem because everything works under linux.
I would assume this is due to some file corruption, but it doesn't make much sense because windows should make some CRC check of its files when installed. Win7 DVD is in decent condition, altough not completely scratch-free, just minor scratchs. Tried to manually remove and reinstall the driver, also downloaded a driver update from Sony's website but it didn't solve anything.
Checking on "Administrative Tools", I could see the log I've attached (change extension to .evtx). It seems there's some problems with ODBC, also some SQL query, and sometimes the registry takes too long to update. I have no clue what could be causing these symptoms and how they could be interfering with wifi, though.

Any ideas? Requests for more info? Any clue on how can I get a new Win7 DVD (preferably free, since I already have the serial)? :P

It SEEMS I have PARTIALLY resolved the issue. After fiddling with older drivers and wireless networks managers with no results, I had the idea to disable all energy saving features of the wifi adapter via Device Manager -> Network Adapters -> right-click in the Ralink (RT3090 i guess) adapter -> Properties -> Energy Management -> untick the box saying the computer can disable the adapter to save energy, or change the "energy saving mode" under the Advanced tab. I guess the wifi card was deactivated when the network got idle, but for some reason couldn't be re-enabled. I could re-enable it a couple times by disabling it on Device Manager and then enabling it again, but sometimes this wouldn't work IIRC.
Another thing I did was to disable the bluetooth network adapters, which I thought might be influencing something, and I don't care enough about them to re-enable them and see if they actually make any difference.

I still can't connect to WPS networks and THIS ISSUE IS STILL NOT SOLVED, but at least connection seems to have stopped dropping all the time for the few hours I've been using it after modifying the settings.

EDIT: well, f***. The problem is still happening, but takes a bit longer to happen. When it happens, though, it seems to be harder to solve than before. My friend even said the problem persisted through reboots.

Trying to reinstall a different version of windows seven from the same DVD but with a different DVD drive. Also cleaned the DVD with rubbing alcohol.

EDIT2: reinstalling windows solved nothing. However, installing both the wifi driver and wifi driver update from Sony website fixed the problem partially, allowing to connect to wps-enabled router and the connection seemed to have stopped dropping. However, after a few weeks, connection started dropping again and things got gradually worse to a point it was unusable for more than a few minutes.