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Hearer is the few steps where we can follow in order to improve
Method 1 :
Also you can try to boot the computer in safe mode and check if you face similar issue
Steps to boot to safe mode:
1. Restart the computer.
2. Immediately after the screen goes blank for the first time, or after the BIOS post ends.
3. Start taping the F8 key repeatedly. The Windows Advanced Options menu appears.
(If the menu does not appear, restart the computer and try again. If the Keyboard has a F-Lock key, it may be necessary to press it first - QUICKLY before pressing the F8 Key. This will have to be done quickly before tapping the F8 key repeatedly.)
4. Select safe mode and press enter
5. Try booting to the desktop
Start your computer in safe mode
http://windowshelp.microsoft.com/Windows/en-US/help/323ef48f-7b93-4079-a48a-5c58eec904a11033.mspx
Method II :
I would suggest you to boot the computer in clean boot i.e. disable non Microsoft services.
The purpose of disabling non Microsoft services is to check if any of these services is
Causing the issue. Follow the steps below to boot the computer in clean boot:
Perform clean boot and check if you have the issue.
1. Click Start, type msconfig in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
2. On the General tab, click Selective Startup.
3. Under Selective Startup, click to clear the Load Startup Items check box.
4. Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All.
5. Click OK.
6. When you are prompted, click Restart.
7. After the computer starts, check whether the problem is resolved.
Reset the computer to start as usual
After you have finished troubleshooting, follow these steps to reset the computer to start as usual:
1. Click Start, type msconfig.exe in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
2. On the General tab, click the Normal Startup option, and then click OK.
3. When you are prompted to restart the computer, click Restart.
If the issue is resolved check which third party is causing the problem, referring the link given below?
http://support.microsoft.com/kb/929135
To help troubleshoot error messages and other issues, you can start Windows 7 by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts."
Sounds like the long load issue in windows 7 I had this a few times. It's a software/driver issue. It's a real pain to fix sometimes. This route is not always a guaranteed fix, but googling "windows 7 long load" gets a number of fixes. It also plagued Vista.
from link "http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/windows-7-is-extremely-slow-to-boot/0fc66916-690a-4901-bc47-adf77e8f3a6f"