This is my stab at putting all the most essential & free PC utilities into a single CD. Everybody loves a compilation!

PART 1: REMOVING UNINVITED GUESTS

All the software listed below is free for personal use, at the time of writing

--- Essential Spyware/Adware Scanners ---

Ad-Aware SE + the latest definitions
Also get the Adaware VX2 Cleaner Add On (to use once installed, go Add-ons > VX2 Cleaner > Run Tool)

Spybot Search&Destroy + detection and library updates

These cover similar ground, but running both is recommended.

--- Stop Future Spyware/Adware ---

SpywareBlaster
Can prevent the spyware being downloaded in the first place. Needs manually updating if you don't pay however.

Microsoft Anti-Spyware Beta
Scans for existing spyware and stops it getting in to begin with. The Beta is free but the full program will almost certainly require a payment. This is getting very good reviews. You need to authenticate your version of Windows to download this.

Bug Off
Closes some loopholes used by browser hijackers to infect your machine.

--- Other Spyware/Adware/Hijacker Utilities ---

CWShredder
Removes all versions of a common browser hijacker called CoolWebSearch.
If this closes as soon as it opens then you may have a variant of this trojan which tries to dodge Anti-Spyware programs. In that case you might need CoolWWWSearch.SmartKiller Removal Tool. Use it, then run all your anti-Spyware programs again!

HijackThis
A homepage hijacker detector and remover, much loved by the pointy headed.

Toolbarcop
A browser extensions manager. Helps remove unwanted Browser Helper Objects (BHOs)

BHODemon
Allows you to enable/disable Browser Helper Objects (BHOs)

--- Anti-Virus Essentials ---

Stinger
Free standalone tool from McAfee that removes many major viruses. New versions are every few months.

Avast! + latest updates
Well respected antiVirus program which is free for home use.

+ Updates for all the main AV software - the PC owner may have any of them (or none!)

--- Other ---

CCleaner (Crap Cleaner)
This deletes redundant files, and thus speeds up any virus/spyware scanning.

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For instructions on what to do with all these programs, read the excellent Major Geeks cleanup guide. My only slight amendments to this would be:

1. If you are in circumstances where the only internet connection available is via a company network, you really shouldn't connect an infested PC to this network. This means the online virus scanners are a no-go. Instead, step 1 should be to run Stinger in safe mode, then update and run a full system scan with an existing Virus scanner, if one exists, or install one (such as the free Avast) if not.

2. Sometimes, removing Spyware can cause registry problems which prevent you from using the internet. In these circumstances, try Winsockfix.