Boot Scan Doubt

Not sure if this should be here or in the Avast Free/Pro section, but since this is dealing with a virus scan, I’ll put it here, sorry if I’m wrong.
My mom runs McAfee total protection on her laptop, whilst I use Avast on mine. Recently, her AV shut down an refused to be reactivated, kinda like when you have a PC in safe mode and just try and turn things on without doing anything else. Anyway, I recommended she use avast to try and hunt down the possible problem. I started a boot scan and so far it’s at 42% having found and removed some 10 malicious files that McAfee never even noticed. Also, many of these are very old files, from the time my sister used to run Limewire on the PC, but I also got hits in the first few percents that were files in the recycling bin, and one or another, but I can’t remember them all just off the bat, though I can post the scan log when it finishes if anyone needs it. Anyway, what I’m a bit worried about is the fact that it was at something like 25% and then suddenly jumped to 40%. What I’d like to know is if this is something normal in the Avast boot-scan or if there’s a possibility that this is being caused by a virus. So far I haven’t taken any other steps to clean the PC, seeing as how avast has been running a full scan and now a boot-scan. I would have run Spybot: S&D, but McAfee removed it from her PC claiming it was incompatible. Oh, by the way, after she installed Avast, she DID NOT remove McAfee since she had to pay for it and all, so I’m wondering if this may be caused by incompatibility between the two. Anyway, I’d like to know about the whole percent jumping thing and also, I’m wondering if anyone here has some advice on possible infections that could have caused the AV to turn of it’s real-time scanner and prevented scans from starting.

Thanks for any help guys.

Well, the percentage jumping can happen, some file types take longer to scan and such, so that could be normal.

But running any scan with both resident AVs installed could cause problems, especially the boot scan.

You want a good on-demand scanner for her, use this>>http://www.malwarebytes.org/products/malwarebytes_free

Hey, thanks for the answer. Anyway, I was considering Malwarebytes, since I myself use that for my PC. Anyway, after the scan finishes I’ll download Malwarebytes and run a scan. I’ll also check to see if McAfee is still stuck or not, I’ll post back later with i it’s working or not. Also, if it’s not working, I can post logs if you need them for any reason.