Hey Gilly,
That model of the Presario comes with a Celeron 633MHz CPU and a 15 GB HDD. While that is a slow processor by today's standards, it is sufficient processing power for what you are running.
It sounds like you definitely have an OS problem. I don't think your memory modules are the problem. They rarely fail and when they do, it almost always results in random system crashes. Same with your CPU and HDD.
The problem likely lies with either the software you have installed, drivers or the OS itself. I could spend hours troubleshooting your software, but unfortunately it looks like your best solution will be a hard drive re-format. I don't like Windows ME as an OS. Windows 2000 is much more stable and has better support and drivers from MS.
When you get a Windows problem like this, it is very difficult and frustrating to try and fix it. Best bet is a clean install. I would backup all data you have on disk or CD and then wipe the hard drive and re-load the OS and your programs. It sounds like a real hassle, but it is not too difficult. I can walk you through the process if you wish.
I would look into upgrading to Windows 2000 though.
As far as spyware goes, there is an excellent free software program available called "Ad Aware" made by Lavasoft. It is free and they periodically release updated reference files for it which you can download for free to keep it current. If you run it frequently, it will keep your PC free of spyware. A must for anyone who surfs the net. I think future versions of Norton Antivirus will also include this feature, however I really recommend Ad Aware.
Here's a link:
Download Ad Aware free