Get BetterSADX.
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=299808681
Select "BetterSADX + Dreamcast Conversion" when installing BetterSADX.

Originally posted by ChocIce75:

Get BetterSADX.
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=299808681
Select "BetterSADX + Dreamcast Conversion" when installing BetterSADX.

What do I do after I install it?

BetterSADX automatically sets the screen resolution to your computer's highest screen resolution. It also enables mod support.
The Dreamcast Conversion mod makes the game look like the Dreamcast version. (the dreamcast version was much better.) Use "Config" to launch the mod manager, where you can enable/disable installed mods. Disable the Dreamcast Characters Pack if you don't want the Dreamcast character models.

How to make my game widescreen without BetterSADX if i want a purely vanilla experience but in widescreen?

Originally posted by DrPeeper(@The Mover Cell):

How to make my game widescreen without BetterSADX if i want a purely vanilla experience but in widescreen?

you can't you have to use a mod installer such as better sadx or sadx mod installer

https://sadxmodinstaller.unreliable.network/

Ok

What about my save file

Originally posted by fluffydonkey1:

What about my save file

Been awhile...But always make a backup just in case it doesn't get transferred over. BetterSadx converts the sava file over anyhow but since it's an old outdated program. Go with Butterwort suggestion. PKR's version is more updated and has more features if that's your cup of tea. Just remember to back up your save file first before giving it a go.