Intel specifies this chip as not having Hyperthreading support.
Speccy v.1.14.288 (64-bit) says:
CPU
Intel Core i5 2500K
Cores 4
Threads 4
Name Intel Core i5 2500K
Code Name Sandy Bridge
Package Socket 1155 LGA
Technology 32nm
Specification Intel® Core i5-2500K CPU @ 3.30GHz
Family 6
Extended Family 6
Model A
Extended Model 2A
Stepping 7
Revision D2
Instructions MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, Intel 64
Virtualization Supported, Enabled
Hyperthreading Supported, Disabled <<<<<<<<< ?
Fan Speed 20 RPM
Bus Speed 99.8 MHz
Stock Core Speed 3300 MHz
Stock Bus Speed 100 MHz