There are several pre-invented wheels you could use for these purposes - I suggest you consider those before building yours.:

• Windows performance monitor already has a mechanism for periodically gathering performance info.
• MRTG can graph the info - and there are contributed mechanisms to import Win PerfMon data
• The underling collection mechanism is ,SNMP, which can get data for both Linux and Windows

In Windows, you will need to add the SNMP service (Add-remove progs -> Win components ---)