The April 2016 results from Steam's latest hardware survey show that Windows 10 is just barely behind Windows 7 among its over 125 million active customers.
In March, the 64-bit version of Windows 10 became the number one PC desktop SKU among the users of Valve's PC game service. However, the combined 32-bit and 64-bit share of Windows 10 still lagged behind the combined users of Windows 7. The new April 2016 numbers show Windows 10 still behind Windows 7, but only by the slimmest of margins. Combining the 32-bit and 64-bit share of Windows 10 shows it now has claimed 39.51% of Steam's users, but the 32-bit and 64-bit versions of Windows 7 are still ahead, with a total share of 39.54%
In terms of individual PC SKUs, the 64-bit version of Windows 10 has extended its lead considerably from March to April. It now claims 38.18% of all Steam users, well ahead of Windows 7 64-bit with 32.53%. The 64-bit version of Windows 8.1 is in third with 11.89%.