I have Windows XP and I downloaded the version before QBASIC 4.5. The QBASIC folder containing QBASIC.exe is in the C:\ drive.

Here's my problem:
I want the window be the full scree3b and not a partial window, so I change the properties, but when I run the compiler, the resolution is very poor and you can see it "shaking" on the screen, as well as the resolution of the text fluctuates from time to time. On top of that, it runs pretty slow.

Sony Vaio (not mine, just temporary) 2.66 GHz
40 GB HD

it shouldn't be slow with the power I have.

Then i'd recommend installing win98 instead of XP.

As ms moves away from 16bit DOS things will probably get harder and
harder for QB

BTW it's QB.EXE not Qbasic.exe for QuickBasic 4.5

If you compile it on 98 then run it on xp you'll probably have better luck
especially with screen 12 if you are using graphics screen mode.