A method of installing an operating system, comprising: determining (S101), in a temporary system, a target physical hard disk to be used for installing an operating system in response to an user operation of specifying the target physical hard disk; judging (S102), in the temporary system, whether the temporary system and the operating system to be installed are of a same type; querying (S103) a logical drive letter of the target physical hard disk on the operating system to be installed by a query way corresponding to the judgment result, wherein the query way comprises: determining a logical drive letter of the target physical hard disk based on a serial number of the target physical hard disk, determining the logical drive letter of the target physical hard disk based on the slot number of the target physical hard disk; installing (S104), in a small system for the operating system to be installed, the operating system on the target physical hard disk identified by the logical drive letter, wherein the determining a logical drive letter of the target physical hard disk based on a serial number of the target physical hard disk comprises: obtaining a serial number corresponding to the slot number of the target physical hard disk, obtaining a correspondence between the serial number and a logical drive letter, finding the logical drive letter corresponding to the serial number of the target physical hard disk from the correspondence. determining (S101), in a temporary system, a target physical hard disk to be used for installing an operating system in response to an user operation of specifying the target physical hard disk; judging (S102), in the temporary system, whether the temporary system and the operating system to be installed are of a same type; querying (S103) a logical drive letter of the target physical hard disk on the operating system to be installed by a query way corresponding to the judgment result, wherein the query way comprises: determining a logical drive letter of the target physical hard disk based on a serial number of the target physical hard disk, determining the logical drive letter of the target physical hard disk based on the slot number of the target physical hard disk; determining a logical drive letter of the target physical hard disk based on a serial number of the target physical hard disk, determining the logical drive letter of the target physical hard disk based on the slot number of the target physical hard disk; installing (S104), in a small system for the operating system to be installed, the operating system on the target physical hard disk identified by the logical drive letter, wherein the determining a logical drive letter of the target physical hard disk based on a serial number of the target physical hard disk comprises: obtaining a serial number corresponding to the slot number of the target physical hard disk, obtaining a correspondence between the serial number and a logical drive letter, finding the logical drive letter corresponding to the serial number of the target physical hard disk from the correspondence. obtaining a serial number corresponding to the slot number of the target physical hard disk, obtaining a correspondence between the serial number and a logical drive letter, finding the logical drive letter corresponding to the serial number of the target physical hard disk from the correspondence. <EOS>