Help needed to help a friend whos system was attacked

A friend of mine has a nightmare laptop issue on his hands I'm tryin to help him with. Needs the computer for work orders with an on the road installation job.

Now to the problem. All i know is it was a virus/spyware type attack symptoms being the net home page was changing at random, web pages jumping around to adds, browser constantly crashing. You know all that fun stuff and to top it off it was loaded with all the junk a retail computer comes with, tons of expired trials, disk clean up and defrag have never been run even once. So i knew it was a mess from the get go.

I installed avast free version and found a couple trojans avast put in the chest and also ran spybot or some program like that was already on the computer which found alot of adware. Then got rid of a bunch of the expired trials and any software or junk not needed and ran disk clean up and defrag. All seemed well after that, computer was responsive again, browser working ok. This was about a month ago.

He bought my old factory computer now about a week ago, just an average gateway, running fine, has had current avast and spydoctor for along time with no major threats or attacks. I guess the laptop had slowly had symptoms i warned them about coming back. As soon as he plugged the comp from me into his routers internet that the laptop had been running on, soon after the computer he got from me goes crazy with the exact same symptoms the laptop is getting.

So tonight I go see if I can help again and find out the laptop had been acting up again shortly after I tried to get rid of the threats a month ago. Both computers are not hooked up to the net at the moment because they just moved. I start by running the spyware and antivirus on both and both find lots of high threats and one type which looked really bad because it's the type that pulls in and sets up more bugs. I got my old comp running ok again, still have some windows settings I need to fix but I pretty sure its cleaned of threats.

The laptop on the other hand is in ruff shape and thats the comp he needs for work because public wireless is a block away the laptop works with. I tried fixing the laptop but it was attacked so bad and is running so horribly that it I don't think I can get it back to normal without some high quality spyware/antivirus and restoration CDs or a complete OS reinstall.

Is this something that can somehow be fixed and if so is it even worth it. It's not all that great of a laptop but it is in great need right now by the owner.

Thank you for reading and any input or advice to get this laptop back on track would be greatly appreciated.