When I try to open that, Windows doesn't know what to do with it.

So tell it what to do.

(double click the file, then select Windows Notepad manually, dosbox.conf is a txt file).

Okay, I manged to open it, and set Usescncodes=false and I still get the ; instead of the :

Open the keymapper, remove the bindings for the shift keys, then try to reassign them (to your shift keys).

kturcotte wrote:

It's a US keyboard (I'm in the US). As far as specs: Intel Pentium 4 3.6 Ghz with Hyper Threading 2 GBs DDR 3200 RAM ATI Radeon […]
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It's a US keyboard (I'm in the US).
As far as specs:
Intel Pentium 4 3.6 Ghz with Hyper Threading
2 GBs DDR 3200 RAM
ATI Radeon X700 Pro Video Card (PCI-Express)
Sound Blaster Audigy 2 ZS Platinum Pro Sound Card
Windows Vista Ultimate 32 bit
DosBox 0.72
DFend Reloaded 0.7.0

Windows XP Media Center 2005, Vista Home Premium, and Vista Ultimate add an extra keyboard driver that screws dosbox up (the wrong layout is assumed once it sees the 109 keyboard). You have to remove that driver (109 key multifunction something keyboard, I have it fixed on all my pcs so I can't look it up) before the keys can be mapped correctly.

Vista Business is unaffected because it doesn't have Media Center; the driver is for some media center wireless keyboard that I have never seen.

usescancodes=false and modifying the keymapper will NOT fix the problem.

This thread covers the Microsoft eHome MCIR 109 Keyboard driver issue in Vista:
Right-Shift / Backslash Keyboard Problems (SOLVED!)