Poptop works extremely well with the built-in Windows PPTP clients. You might also want to have a look at OpenVPN.
poptop is terrible. It has all kinds of performance issues to the point where it's basically useless. This was maybe 6 years ago I tried this out, and they haven't released an update in that time period either, if that tells you anything. If you want to do a PPTP server, use the one in windows server.
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