Hi Lukaz,
We are using the Designer studio 1.5 sp also. our Desktop spece is in below, we have no issue and it works fine.
Window 7 Enterprise 64-bit.
CPU: Intel i5 4 Cores
Memory 4 GB
Are you using Designer Studio for Windows X64?
You may use perfmon to monitor the load on your VM to find the bottleneck. It may be the Disk I/O issue.
