Well after reading just the first post I can already tell you that you are in fact infected. Wanna know how I know this with just a simple read?
You were browsing the Windows.old folder. Right there tells me that the system was not properly formatted when you reinstalled leaving all of your old files in tact. Thus when you were browsing the folder, you got infected again hence the warning. Now your system is infected and it wont operate properly to get rid of it.
The reason for the crashes could be due to the infection. It could just be that they are causing the system to work itself into a circle and get a kernel panic and crash. Could be that they are causing the kernel to crash. Either way this infection you have is causing your problems.
You did not get this problem after you formatted cause you didnt go into the windows.old folder. Now that you did you activated the infection again. Notice the pattern?
You have to get rid of that Windows.old folder first and foremost. From there you need a god cleaning of the system.