Everytime i set any website address as a homepage in IE7, the next time i run IE...the homepage disappears and the entry of HTTP:/// come in automatically.

how to fix this issue? I've checked the PC thoroughly and there is no virus on it.

Might not be a virus that's causing this.

Download some anti-spam software and check its not a spyware hijacker thats taking control of IE7.

"Adware Anti-Spam" is good for tracking this kind of thing. If you know what you doing, you could always use "HiJack This".

okay i'll try HijackThis

First scan for malware, using AntiVirus and also AntiSpy. Then use CCleaner to clear PC junk. Reboot.

Next: Open Regedit and navigate to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\URL\DefaultPrefix
Now, in the RHS, double click the Key "(Default)" and ensure that its value is set as: http://
If not, then change its value to : http://

Next, navigate to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\URL\Prefixes
Again, in the RHS, double-click the key "www" and ensure that its value is set as: http://
If not, then change its value to http://
Click OK. Exit Regedit. Reboot.

Now try to set the home page, and see if it has helped.