Well, the first thing is to identify what drivers you need. W7 has a pretty full set, but there will still be some you'll likely need.
First thing: you need to find out the manufacturer/model number of your motherboard. I use Belarc Advisor, but there are other tools.
Once you know that, you need to find the motherboard manufacturer's web site and look for drivers for your board. You may well find them under 'support'.
A good way of finding out which drivers your PC is missing is Device Manager (start, Control Panel, Device Manager). Anything that's listed there with ayellow exclamation mark needs a driver. Ihose may include chipset, Network adapters/LAN and audio.
If you have e.g. an external graphics card, you'll need to locate the drivers for that too.
Download the drivers you need - ensure they're W7 drivers - and put them on a USB key. Then transfer that to your PC. You can execute the drivers - most come with a 'setup.exe' file - from the key by double clicking on them.
Do the above, and let us know how you get on.