I've made a fresh standard installation of Qubes OS on a Lenovo SL510 with 220 GB memory. A reclaimed all disk memory during the installation to whipe out my previous Debian installation.
However, whatever I do, for instance open firefox on my personal VM, I get the message "Not enough memory to start VM. Close on or more running VMs...."
Could somebody give my some step-by-step instructions on how to solve my problem?
/N
Your computer doesn't have 220 GB of memory. You have 220 GB of disk space. Assuming your computer is the Lenovo X220, you probably only have 4 GB of memory in this machine, as this was the amount the machine was sold with back when it came out.
Unfortunately, 4 GB will not get you very far with Qubes. You can do wotk with 8, but you really need 16.
> Could somebody give my some step-by-step instructions on how to solve my problem?
I've googled a bit, and it seems as though the X220 supports up to 16 GB, so the solution for you is to buy a memory upgrade. It should be reasonably cheap.