Do you happen to have a antivirus software? If so, please update your antivirus software and do a scan of your PC in safe mode.
I also recommend you to do a online scan.
Please go HERE
to run Panda's ActiveScan
- Once you are on the Panda site click the Scan your PC button
- A new window will open...click the Check Now button
- Enter your Country
- Enter your State/Province
- Enter your e-mail address and click send
- Select either Home User or Company
- Click the big Scan Now button
- If it wants to install an ActiveX component allow it
- It will start downloading the files it requires for the scan (Note: It may take a couple of minutes)
- When download is complete, click on My Computer to start the scan
- When the scan completes, if anything malicious is detected, remove the malicious item
If you are still having problem or you feel that there is still some more things resides in your system, then do this.Preparation Guide For Use Before Posting A Hijackthis Log
After you have done with the preparation, then post a new topic in HijackThis Logs And Analysis
Also note that, missing taskbar/start menu can have various cause. While I do not know which one, from your post description, I recommend you to do the above before we look into other solution.