In everest it should be under video display adapter
You don't say what OS you are using but i will assume xp for now .
right click on your desktop/properties/settings/advanced /adapter ,look for memory size .almost the same for win98,
Onboard video uses you systems ram so you could right click on mycomputer /properties ,and you will see info on you processor and amount of ram ,if you know how much ram is in your computer then subtract the amount showing from the amount in you computer ,and that will be the amount of ram being used for video .
It will also tell you in the Bios but i won't go into that .