I compared the slow boot  with the previous one using the BootRevealer.
The problem began after starting the Session Manager:
I checked the most often used files.
Here I found the strange results:

Who needs the Hiberfil.sys? Surprise.

Detailed activity log:

Seems like the process reads the data from ‘hiberfil.sys’ and writes to ‘System Volume Information’. It is about 370 Mb read and the same written during normal Windows boot-up.
But why?
Who is need the ‘hiberfil.sys’?
I did not use hibernation at all.
The Windows system uses standard “balanced power plan” with sleeping after 30 minutes of inactivity. Hybrid sleeping is disabled.

Another strange thing:

The written file is deleted.

I explored the event log:

Event Source:                  VolSnap
Event Category: None
Event ID: 25
Volsnap driver is related to Microsoft Volume Shadow Copy Service.
Here is a great article about it:
http://technet.microsoft.com/en-us/magazine/2006.01.rapidrecovery.aspx
I have no problem with free disk space on the drive: 450 Gb is free, 14.8 Gb is used.

Looks like the problem is in high load:
http://support.microsoft.com/kb/826936
“Shadow copies are lost during backup and during times when there are high levels of input/output”.
Of course the Windows boot-up process is not good time for backup.
It is very strange for me, why the VSS did not wait for more comfortable time.
As a result I had the boot delay and lost all restore points.
Looks like there is no hotfix of the problem for Windows 7.

One positive thing: I know what happened.
There is not any  secret in the Windows boot-up process.
As workaround, I  turned off ‘hiberfil.sys’, because I don’t use it,  using the simple command:
powercfg -h off
Also, I know how to turn it on: powercfg -h on