(Note "480i" could refer to either analog or digital video.)
If your "old television" accepts what you call a "480i" signal, then that would presumably be an analog composite video signal (aka CVBS) of 525 interlaced lines. The input connector on the TV would probably be an RCA jack, color coded yellow.
The straight-forward solution (if there are no other TV inputs like component video or DVI or HDMI) is to use a VGA-to-composite video converter. Typically the converter will accept a VGA resolution of 1024x768 for a reasonable-sized Windows desktop. Video images on the TV will look good to okay, but reading menus and text will probably be difficult (or near impossible if it's a low quality TV). Do not bother trying a cheap "VGA-to-composite adapter cable"; it simply won't work if you read the fine print.
Even if you could get your laptop to output 480i (640x480 interlaced), the Windows desktop would be very small but with huge icons. Try Safe Mode at 800x600 and you'll get an idea. That's why Windows 7 does not allow low resolutions less than 800x600. BTW some video adapters can output an interlaced "VGA" (e.g. 1080i on some nVidia cards using "custom resolution").