That's not true. The Time Capsule allows any computer to see the HDD, regardless of the format. I have my TC connected to an XP and a Vista computer and both can see and access the TC's HDD flawlessly even though the HDDs in the TC are HFS+
What you need to do is add the TC's IP address to any software firewalls installed on Vista. Just add 10.0.1.1 (or whatever IP you've assigned) to the list of trusted networks/zones. Also, be sure to include the workgroup name that your machine is a part of in your TC's setup. Go to Manual Setup > Disks > File Sharing and you'll find a field for your Workgroup name. If that fails, there's a disc that came with your TC. It will have AirPort Utility for Windows. Install that and it will place an icon in your taskbar (AirPort Base Station Agent) which will let you connect to your Time Capsule's HDD.