WIERD hijackthis not installing

hi
my computer has been invected with back door type virus. the symtoms are:
1. i first noticed the CPU processing spiking every 7 seconds by 40-50 percent, when i had no programs running.
2. web pages refering to hijackthis and process explorer close immediately.
3. i have managed to download hijckthis in a zip. but after unzipping there is nothing in the folder
4. i downloaded and burnt both hijackthis and process explorer to a CD on friends MAC. when i explore the CD on my machine the CD appears empty.
5. tried to install bitdefender but as i was installing it the installation stopped when it was "starting services".
6. i have done some online virus scans and they have found files relating to a virus. the file was something like bkdr hacdef. the scan also found a couple of trojans.
7. regedit would only open in safe mode, i renamed regedit it now works, but another regedit has appearded?


does anyone know how i can fix this or point me to a thread that will help

 

Here's a direct link to an unzipped version; try that one:

https://www.wilderssecurity.com/supportfiles/HijackThis1980hf.exe

 

i tried the link, but i could not save the file to disk. it seemed to download it but once the progress bar reaches 99% i get a message cannot copy file: cannot read from the source file or disk

 

Click on the link in my signature and follow the instructions there.
Also open your hosts file and remove all entries that doesn't belong there.

 

still not much joy

im scanning my drive avast which i found on that last link

i just recieved this warning from an antivirus software i installed yesterday

C:\WINNT\HXDEFDRV.SYS

Contains a signature of the (dangerous) backdoor program BDS/HacDef.073.B.1 Backdoor server programs

what is this backdoor server program?

i still cant download hijackthis

Artras i dont know what you mean by "open your hosts file and remove all entries that doesn't belong there" how do i do this?
^
Artras ignore the above line i have just read up on hosts. i didnt remove entries the dont belong there i i changed thier IP to my local host. i have read that this blocks them.

 

this the avast cleaner tool log

avast! Virus Cleaner Tool - version 1.0.197 Unicode

21/07/2004, 13:36:46
Memory scanning started...
No virus body found in memory.
Memory scanning finished (15.7s).
----------
Files scanning started...
C:\Documents and Settings\Administrator\Local Settings\Temp\~DFD42F.tmp... file could not be scanned!
C:\RegProt\regprot.exe... file could not be scanned!
C:\WINNT\hxdefdrv.sys... file could not be scanned!
No virus body found.
Files scanning finished (66278 files, 0 infected, 2377.0s).
Drives scanned: C:
----------

i deleted C:\WINNT\hxdefdrv.sys
should i delete ~DFD42F.tmp?