First of all, which antivirus software are you using? I didn't see it running in your HiJackThis log.
Second, make sure Windows Firewall, or a similar firewall is enabled.
Onto the log:
Fix the following entries using HiJackThis:
F3 - REG:win.ini: load=?????? ??????????
O2 - BHO: Core Library - {A23AB93D-6CFF-442c-BB8A-41F6145F47E7} - C:\WINDOWS\System32\PDF06d4.dll
O3 - Toolbar: (no name) - {EF99BD32-C1FB-11D2-892F-0090271D4F88} - (no file)
O4 - HKLM\..\Run: [WildTangent CDA] RUNDLL32.exe "C:\Program Files\WildTangent\Apps\CDA\cdaEngine0400.dll",cdaE ngineMain
O4 - HKLM\..\Run: [Vga Locks Manager Global] C:\Documents and Settings\All Users\Application Data\find bags vga locks\binddrv.exe
O4 - HKLM\..\Run: [SafeGuard Popup Updater (required)] regsvr32 /s C:\WINDOWS\System32\PDF06d4.dll
O4 - HKLM\..\Run: [Popup Defence Updater] regsvr32 /s C:\WINDOWS\System32\pdfupd.dll
.exe
On a lighter note, I do not recommend System Mechanic or any other "PC mechanic" software. Using MicroBell's 5-step process is good enough, and cleans your PC, instead of damaging it.