2ivan: curl is the CURL exe (http downloader). You need libcurl, not curl. I suspect, curl is not needed in this case. Please try to use the latest package -- the version is encoded in a zip name. Well, we'll probably correct the packages list to not include curl.
I run win7 with 768 MB of RAM set. You can try disabling different visual effects and disable Aqua and set it to use "Classic" theme only. Anyway, we haven't 3D acceleration support, so that is a waste of resources. So, I did like this. WinXP SP3 is optimal to run on OS/2 host, it almost "flies". I set the VM RAM size to be 512 MB. Didn't seen any critical errors. Maybe, you have VAL too little (I have VALIMIT=3072 on my machine with 3500 MB of RAM available and VALIMIT=2500 on a machine with 3000 MB of physical RAM available). Also, I was not able to set more than 1700 MB of RAM to a single VM. The limit of RAM usage by applications is about 2100 MB. If I try to set more, the VM just panics (Guru meditation). This is a result of lack of available address space (remember that OS/2 is a 32-bit OS and Shared memory occupies some space in virtual memory, so, less private memory available, and vice versa).
Yes, .vhd is VirtualPC disks and can be used with VPC.