I'm adding that before doing anything, back up hosts. Copy and paste it somewhere you can access it, but rename it hosts.bak. Should you open the hosts file, open with notepad.
If you can, could you post your hosts file here? That way we could tell if something malicious is in there or not.
And here's a quick reference to what you SHOULD have at minimum in the hosts file should you decide to look at it.
(From Microsoft website)
All that's there is the local host, which is just a self referencing IP. You shouldn't have anything else below it.
# Copyright (c) 1993-1999 Microsoft Corp.
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
# For example:
# 126.96.36.199 rhino.acme.com # source server
# 188.8.131.52 x.acme.com # x client host
You can actually add to it and block other sites (stop common ad-ware dead), but I'd recommend against doing that unless you know specifically what you're doing.
When you're done be EXTREMELY careful how you save hosts. In notepad, when you decide to save, select SAVE AS and when the save window pops up, use the drop bar at the bottom where it says 'Save type as' and select ALL FILES. Name it 'hosts' with no dot anything, just the name itself and that should replace whatever old thing was in there.
If this doesn't work, you could have something re-directing you in your registry files.
But please get back on this before tampering with the registry.