From the link Nepatsfan (congrats on 16-0, BTW!) and Ken gave:
"To replace Microsoft software that was distributed with your computer
by an OEM or a System Builder, contact the OEM or the System Builder
directly."
Years ago, I purchased a custom-built PC. I, too, lost my installation
disc. I contacted him, and he promptly mailed me a copy of a generic OEM
install disc, which can be used with one's product key. If you don't
know your product key, you should be able to retrieve it by using Belarc
or Magical Jellybean Finder:
(1)
http://www.belarc.com/free_download.html
(2)
http://www.magicaljellybean.com/keyfinder.shtml
Once you have your key, write in down and stick it to your PC's case!
Hopefully, you will be able to obtain a generic OEM disc, too, without
having to purchase a brand new one. Although it's possible to download a
torrent, I can't recommend this method because there's no guarantee it
will be free of viruses, rootkits, etc. Instead, maybe you can find
someone (a co-worker, friend, relative, neighbor, etc.) who has one.
Then you can make a copy.
Worst case scenario is that you will need to purchase another
installation disk, which should cost under $100. But let this be a last
resort.
Although the most certain method of cleaning a thoroughly compromised
system is to perform a clean install, you first may want to try
something less drastic. The many things you tried certainly haven't
worked yet, so let's start from scratch:
Malke's page has a lot of useful information:
http://www.elephantboycomputers.com/page2.html#Viruses_Malware
Basically, you need to address viruses, worms, trojans, etc. *and*
non-viral malware (spyware, etc.) I know you already know this, but
since your methods (which you didn't disclose) haven't yielded
satisfactory results, I'm mentioning it.
For the first part of the equation, many people have had success with
David Lipman's Multi AV Scanning Tool:
http://www.pctipp.ch/downloads/sicherheit/35905/multi_av_scanning_tool.html
Although the page is in German, the tool is in English.
Personally, I've been very happy with AVG Free:
http://free.grisoft.com/doc/2/
Others have reported that Avast is a very good antivirus app:
http://www.avast.com/eng/avast_4_home.html
(By the way, all the links I'm giving you are for freeware.)
And for spyware, there are many fans of SUPERAntiSpyware Free:
http://www.superantispyware.com/superantispywarefreevspro.html
Personally, I use Ad-Aware and Spybot Search & Destroy to handle
spyware:
http://www.lavasoftusa.com/products/ad_aware_free.php
http://www.safer-networking.org/en/spybotsd/index.html
If you're interested in *preventing* spyware from entering your PC,
SpywareBlaster is a good app:
http://www.javacoolsoftware.com/spywareblaster.html
One final suggestion is to run HijackThis (if you think you may still
have more malware). Download it from:
http://www.spywareinfo.com/~merijn/programs.php
and post the log to an appropriate forum, such as:
http://www.bleepingcomputer.com/forums/forum22.html
Here's a helpful tutorial:
http://www.bleepingcomputer.com/tutorials/tutorial42.html
Once you are satisfied that you are malware-free, there are other steps
you can take to speed up your PC. First of all, you need to determine
if you have enough RAM for how you use your PC. Press Ctrl+Alt+Del to
open Task Manager. Click on the Performance tab.
Look under Commit Charge (K) in the lower left-hand corner. What are the
values for Total, Limit, and Peak? Also, how much RAM *do* you have?
If you don't have enough memory, you will find Windows will start using
the pagefile frequently, which slows everything down.
Last suggestion:
Take out the trash (clear temp files) and defrag the hard drive if you
haven't done so already. There are a few different ways to clear away
temp files from within Windows (Disk Cleanup, for instance). I
personally like Ccleaner, which has a very user-friendly interface:
http://www.ccleaner.com/
Just use the main feature of cleaning temp files. Don't use the Issues
feature (not necessary and it's possible it might mess things up!).
Good luck!