While installing, select "format disk." Do not check "use existing partitions" as your option. It will warn you all data on this disk/partition will be lost. Sounds like you're okay with that. In my case, it wouldn't let me format the entire disk. I had to check "use existing partitions." However, if you select BOTH partitions to format, it will wipe Win-Don'ts from its own partition.
You may need to do this from either a liveusb stick or a livecd running on an external usb dvd drive.
I've been running PCLOS-only on my tiny 8gig flashdrive Aspire One for about a year now and never looked back. Occasional glitches, but nothing the forum couldn't quickly fix.