It would appear that at least one system file is corrupt since SFC is asking for a clean source. Without the Windows CD, you can point it to: C:WINDOWS\System32\Dllcache (assuming C: is your system root which it probably is) and sometimes that will work. If not, then the next logical step is to redownload and install SP2, I hope you are on broadband, since SP2 over writes most of the original OS files.
Before you do that, I see this entry in your HJT log for an installer. I don't know what it is, do you?
O4 - HKLM\..\Run: [LanzarL2007] "C:\DOCUME~1\OWNER\LOCALS~1\Temp\{91EFC222-7C9F-4090-9ADC-47FB3FF9B003}\{D1DA2BA7-2592-4036-9BB2-DCCABDE8DC1A}\..\..\L2007tmp\Setup.exe" /SETUP:"/l0x0009"
If the answer is NO, let's get rid of temp files (make sure that goes).
Go to Start>Run>type in %temp% hit Enter and delete the content of all the temp folders shown (only the content, not the folder). A couple of files may be in memory and will not therefore delete, this is normal.
Try the ComboFix again now before going to Windows Download site.