Windows – External speakers don’t work in Windows 7

I'm having a peculiar problem. There is no sound coming from my external speakers. I have an Asus EeePC 1215B with an external set of speakers. And while the onboard speakers of my laptop work perfectly well, and while windows 7 recognizes it when I plug in the analog 3.5mm jack to the external speakers, no sound comes out.

I know it's not a hardware problem. I have a dual-boot system, and this EXACT hardware setup works perfectly fine under my linux distro.

I have checked and double-checked all volume and mute settings. No mute is on, and volume is up (yes, also the physical volume button on my external speakers). As soon as I unplug the 3.5mm jack, my on-board speakers work fine. As soon as I plug it in, silence.

I have updated my audio drivers, both from microsoft and from the asus website. I've rolled back, upgraded again, and this didn't solve the problem.

Under playback devices, my speakers show up. They are set as default device (the other is my HDMI, which I don't ever use), and the green bar to the right actually lights up when sound is played. It just never leaves the speakers.

Again, Windows does recognize the external speakers. Realtek HD Audio Manager pops up whenever I plug it in, and the onboard speakers are muted (as they should be).

I would appreciate any and all help you can give me, since I'm out of ideas. If more information is needed, I'd be happy to provide it. Thanks in advance!

Forgot to mention: I don't get any error messages anywhere. Not in the playback devices, nor in the device manager. Nothing errors at all.

@Ariane: I've tried. I've uninstalled it from the device manager with the speakers plugged out, then installed the Realtek HD Audio driver from the asus website (version 6.0.1.6293). After a restart, Windows informed me (in the lower right) that it was installing an audio driver. After that, no change in the behaviour (on-board speakers work fine, plugging in my external ones silences everything).

@CarlB: No, the only tabs I see in the Realtek HD Audio Manager (I hope that's what you mean, I cannot find anything literally named "Realtek options") are the "Speakers" and the "Microphone" tabs.

The Realtek HD Audio Manager does pop up when I plug in the 3.5mm jack, and allows me to select whether they are headphones or speakers. Both options don't work.