I have already installed other cleaners like "Registry Optimizer", "Regseeker", and "Registry Bot" so far they all find different problems and don't seem to fix or remove any of them. My OS is windows 98 and my computer is a Compaq and it is a little on the older and slower side. Any and all help would really be appreciated.

I heard that if you download an antivirus program and another antivirus program while the old anitvirus program is still installed, your computer would be all messed up and glitchy. Right Now I have Avira, but Avira doesn't fix the RUNDLL Error, and I look at yahoo answer, nothing work, and youtube too.

So if I download a Registry Cleaner and installed it while Avira is installed, would my computer be messed up? What happen if I download a spyware, malware, registry cleaner, and an antivirus program? What would happen with my computer with all these programs? Since Avira doesn't protect spyware, malware, and doesn't do a registry cleaner.
What would happen if I download with anything in any particular order.

A friend of mine keep telling me to download the registry cleaner from free file storage on the internet for free. I need to know is it safe, because i heard that most hack software is bind with trojan. Is it true?
What is the good point in choosing a licensed registry cleaner? Please don't mentioned the brand name.

i installed A GAME WHICH IS PLAYABLE FOR ONLY 2 DAYS, NOW I WANT TO REINSATLL IT AGAIN, BUT FOR THIS I HAVE CLEAN THE REGISTRY. PLS TELL FROM WHERE I CAN GET A FULL REGISTRY CLEANER DOWNLOADS.

Can I have 2 registry cleaners on my computer?