As you've presented it, you only care that the laptops are active. Is that the case? I.e. you want to filter out all tablets, regardless of their state and you want to filter out active laptops. Charles.X has assumed, and I'm going to assume the same, that you want to include active devices and you want to filter out laptops and tablets.
I'm going to offer a small twist on Charles.X's suggested
WHERE
tblAssetCustom.State = 1
AND ( tblAssets.AssetName NOT LIKE '%LAPTOP%'
AND tblAssets.AssetName NOT LIKE '%TABLET%')
Or, since the parentheses are redundant because everything is being ANDed,
WHERE
tblAssetCustom.State = 1
AND tblAssets.AssetName NOT LIKE '%LAPTOP%'
AND tblAssets.AssetName NOT LIKE '%TABLET%'
If you pull the NOT out, you can phrase it more in line with what it looks like you were thinking:
WHERE
tblAssetCustom.State = 1
AND NOT ( tblAssets.AssetName LIKE '%LAPTOP%'
OR tblAssets.AssetName LIKE '%TABLET%')