Operating System Fails To Respond

Upon booting up my laptop, everything seems fine at first. My desktop loads as does any startup programs as normal for a good few minutes until the startup procedure is finished, then simultaneously any programs I have open fail to respond and after a few more minutes my operating system fails to respond. Between the time of the programs and the operating system failing to respond, I cannot execute any other programs nor can I lauch task manager (CTRL+ALT+DELETE etc.). A while after the operating system fails to respond this error pops up, no doubt as a response to me trying to open task manager:"Failure to display security and shut down options. The logon process was unable to display security and logon options when CTRL+ALT+DELETE was pressed. If the operating system does not respond, press ESC or restart the computer by using the power switch."

All this occurs without fail everytime I boot up as normal.I can boot up my laptop in Safe Mode with success which has allowed me to try a number of things but I am no computer tech so my knowledge is slim to none. These are what I have tried:

1) I have run anti-virus and anti-malware programs which came back clean.

2) I have tried to go back to a system restore point but apparently I have none.

3) I have tried a clean boot up (with only Microsoft start up procedures) but did not help, just made my OS fail to respond almost instantly as my desktop loading instead of after a fair amount of time.

4) I have 'restarted winsock' on a forum suggestion from another post it may be a particular virus and rebooted but this did not help.

5) I have turned off UAC and rebooted incase something was making changes causing Windows to fail to respond from another forum suggestion. This did not help either.

6) Rebooted with last known working configuration option.

I should also point out I have not recently added any hardware or software that could make this occur. However, maybe the last 3 things I did before the problem occured could help explain. Firstly, I ran a full anti-virus scan with AVG which removed a rootkit and deleted something 'malicious'. After that I used AVG PC tuneup to clean the registry, defrag and clear junk files. Lastly, I tried to run Steam which froze on an update and I tried to restart my laptop, which froze on the "Logging off..." screen for ages by which time my laptop battery must have died. After this the problems arose.

I really want to avoid anything which might have to result in my reinstalling Windows 7 as my laptop came with it pre-installed so I do not have a Windows 7 disc or a OS backup.

Laptop:- Sony Vaio VPCEA3M1E, Intel Core i3.
OS:- Windows 7 64bit Home Premium