WinTools has infected your computer:
Disable System restore as per the instructions here.

Reboot into safe mode

Click on "Start" => "Control Panel" => "Administrative Tools" => "Services".

Look for a service called "Wintools for IE Service" => Double-click it to open, then click on the Stop button and change the "Startup type" to Disabled. Do not worry if the service is not listed.

Press Ctrl+Alt+Delete once => Click Task Manager => Click the Processes tab => Double-click the Image Name column header to alphabetically sort the processes => Scroll through the list and look for "WtoolsA.exe", "WToolsS.exe" and "WSup.exe". If you find the files, click on them, and then click End Process => Exit the Task Manager.

Go into "Add/Remove Programs" in the "Control Panel" and look for any Wintools entry. Uninstall it.

Open a command prompt by clicking on "Start" => "Run" and type in cmd and click on "OK". At the prompt, type regsvr32 /u /s "C:\Program Files\Toolbar\toolbar.dll" (Quotation marks must be typed in on the preceeding command) then <ENTER>
.
Type exit to close the command prompt window.

Delete the following directories:

C:\Program Files\Common Files\WinTools

C:\Program Files\Toolbar

Run HijackThis, click on "Scan" and then place a check mark in the following boxes, And click on "Fix Checked":

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = file://C:\WINDOWS\System32\SearchBar.htm
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://red.clientapps.yahoo.com/customize/ie/defaults/stp/ymsgr*http://my.yahoo.com
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://red.clientapps.yahoo.com/customize/ie/defaults/su/ymsgr/*http://www.yahoo.com
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = about:blank
R1 - HKCU\Software\Microsoft\Internet Explorer\SearchURL,(Default) = websearch.drsnsrch.com/q.cgi?q=
O2 - BHO: (no name) - SOFTWARE - (no file)
O2 - BHO: BHObj Class - {00000010-6F7D-442C-93E3-4A4827C2E4C8} - C:\WINDOWS\nem219.dll (file missing)
O2 - BHO: (no name) - {87766247-311C-43B4-8499-3D5FEC94A183} - C:\PROGRA~1\COMMON~1\WinTools\WToolsB.dll
O2 - BHO: Band Class - {C5183ABC-EB6E-4E05-B8C9-500A16B6CF94} - C:\Program Files\SEP\sep.dll
O3 - Toolbar: Band Class - {C5183ABC-EB6E-4E05-B8C9-500A16B6CF94} - C:\Program Files\SEP\sep.dll
O4 - HKLM\..\Run: [WinTools] C:\Program Files\Common Files\WinTools\WToolsA.exe
O16 - DPF: {1D4DB7D2-6EC9-47A3-BD87-1E41684E07BB} - http://imgfarm.com/images/nocache/funwebproducts/ei/CursorManiaInitialSetup1.0.0.8.cab

Reenable System restore as per the instructions here.

Reboot and sign in as per normal and post a new HijackThis log for further review.