Vista - Slowed to a crawl....

OK im a newbie to these forums and im a very inexperienced person with computers but here is my problem.

My laptop became infected with trojans and spyware because of a doggy download which opened a hole for this stuff to spread. That rouge software winPc defender installed itself onto my computer. Although I was able to get rid of that pretty quickly and other stuff as well (using norton360, spybot and spyware doctor) that annoying "Insecure Internet Activity. Threat Of Virus Attack" message kept coming up, I also found that whilst using google i would be redirected to pages not relevant to what a had search for (such as blinkx or myspace video)

Using smitfraudfix I was able to remove that message But since I have used smitfraudfix my laptop has been running very slowly and has been crashing and failing seemingly at random. Whenever i try a google search on IE7 it still directs me to blinx and other places that I DID NOT type into the search engine and so I began to lose patience and I downloaded firefox3.

Despite countless scans and checks nothing ever comes up so I suspect some spyware or malware may have sneaked its way undereath so that it is virtually impossible to detect.

Any suggestions on what I may have done wrong and how I can get my laptop to run as smoothly as possible? (In plain English preferably)

You still have malware on computer, and/or your Hosts file is corrupted.

I suggest IE8 with has built in antimalware/antiphishing and smartscreen

Try these:
ESET SysInspector

Download and Install NOD32 4
Free Antivirus Download from ESET

Run Windows Defender (full scan)
Start> in search bar type defender>click program

run Malwarebytes (this will detect polymorphic malware)
Malwarebytes.org

note-Malwarebytes
This is a On demand Scanner only (real time detection mode disabled in free version)
This is a specialized tool specifically targeted at polymorphic Malware, and as such is not very effective against other malware threats. It is also meant to be run in conjuction with installed Antivirus- not as a standalone app

further note-
Chances are you may have suffered Windows corruption that only a repair/re-install may fix.
barring that, and you use the above tools to clean your system, you can improve speed and performance here:
How To Make Vista more responsive and faster

How would I go about re-installing vista? Would this cause me to lose all of the files currently on my laptop at the moment? Its looking that is the only option to have a fully functioning system again.

You dont do file backups? I would do that before you reinstall as i recommend you delete all partitions on your drive and re-install Vista into the unpartitioned space.

start>type, backup>click "backup and restore center" follow prompts.

this will take many DVD's, 1 or 2 BD's, but is recommended to backup to external or other HDD

Clean Install with a Full Version of Vista
Clean Install From Upgrade Vista

OK I understand about backing everything up, but still how do I re-install vista?

If you have a disk, or oem recovery disks see tutorials above in last post of mine.

essentially you put disk in drive, restart, hit any key at prompt, boot into disk, and follow prompts.

If the install hangs or stops after files loaded... that may mean you need to install SATA driver.