First, go to add/remove pgms and uninstall MyWebSearch, then delete the pgm folder of that name.
This is your main problem :
O4 - HKLM\..\Run: [startdrv] C:\WINDOWS\Temp\startdrv.exe
And then there is this, a pest:
O8 - Extra context menu item: &Search - http://edits.mywebsearch.com/toolbaredits/menusearch.jhtml?p=ZKxdm021YYGB
-fix both with hijackthis, then delete the file C:\WINDOWS\Temp\startdrv.exe [you may have to do it in safe mode....]
Alternatively you could download Unlocker to delete it...
If it returns you could try Combofix:
==Download this file to your desktop: http://download.bleepingcomputer.com/sUBs/ComboFix.exe
- to run it dclick combofix.exe and follow the prompts to start it. When finished, it will produce a log, C:\Combofix.txt - post that log in your next reply.
A word of caution - do not touch your mouse/keyboard until the scan has completed. The scan will temporarily disable your desktop, and if interrupted may leave your desktop disabled. If this occurs, please reboot to restore the desktop.