KernelEx and Anti-Virus
I've tried KernelEx with Windows ME and found that it does allow *some* software designed for Windows 2000 and XP to rum, but certainly not all. If you read the documentation, there is a small number of programs that are officially supported by KernelEx, although other software will work. KernelEx provides *some*, but not all, API's for Windows 2000/XP on Windows 98/ME. KernelEx seems to have particular problems with utility software that accesses the internals of WIndows instead of just using common API's. From what I've read on the forums supporting KernelEx, anti-virus software falls into this category of using low-level drivers to intercept system activity and does not just rely on the API's, so that anti-virus software that requires WIndows 2000/XP and newer will not run on Windows 98/ME with KernelEx. I don't want to discourage anyone from trying to use KernelEx, as it is a useful bit of software for Windows 98/ME users.
I believe that avast! is still providing virus definition updates for avast! Home version 4.8, although the last program update to v4.8 was back in November of 2009. avast has kept saying that they will be pulling the plug on the virus definition updates for v4.8, but so far, they have continued to make them available. (it's been a couple of weeks since I booted my Windows ME system, so I can't positively say that the updates are continuing at this time.
As mentioned earlier in this thread, ClamWin is available for Windows 98, but it does *not* provide real time scanning of system activity, and so would best be used as a tool to get a second opinion of an anti-virus with real-time scanning abilities. However, I had problems when performing on-demand system scans with ClamWin on my Windows ME system, as ClamWin would freeze up partway through the scan. A review of the ClamWIn forum found some messages posted last year by someone running Windows 98 who had the same problem as I did. There was never a resolution to this problem posted.
There are a couple of paid anti-virus products that are still available for Windows 98/ME. The first is a product called Protector Plus Desktop 2011 by Proland Software in India. Their current 2011 edition of their anti-virus products still supports Windows 98 and ME. It is reasonably prices at $25 for the first year, and $12 to renew each year thereafter. However, I found this anti-virus to product *many* false positives while missing some true malware. And they never responded to any of the emails that I sent to them. So I would be reluctant to trust this product.
There is a Russian anti-virus product called Dr. Web. The current version is v6, but you can obtain the prior v5, which supports Windows 98/ME. However, after downloading and installinga trial version of it on my old Windows ME system, I found Dr. Web to run extremely slowly, and to place a great burden on my AMD 2200+ system.
Finally, BitDefender, a very reputable anti-virus vendor told me that I could buy a license for the current version 2011 anti-virus, and then contact them to get a copy of their older version 10, the last to support Windows 98/ME. I installed a trial edition of BitDefender on Windows ME and found it to be extremely fast. The only problem I experienced, was that whenever I tried to shutdown or restart Windows ME with BitDefender installed, Windows would freeze up and I would have to power off the system by cutting the power to the PC. I never pursued this to see if there was a way to resolve this issue.
So for now, I'm still using avast! Home version 4.8 and hoping that the virus definition updates will continue for the near future.