Do you use Lightroom? (If not, no point reading further - although you could download the trial and do it in the trial period!)
If you do, bung everything in a big catalogue (if it isn't in one already) then use smart collections to make that huge job more piecemeal.
1. Create a smart collection with a filter that is "doesn't have" and then whatever your keeper flag will be. It could be a green label, or a star, or a keyword of "keeper". This is your list of images that haven't been looked at yet. Your "to do" list.
2. Set a filter to "hide rejected images"
Start to go through your images.
If you want to keep the photo, give it the keeper rating (star, green label, keyword etc). It will be removed from the smart collection.
If you want to reject the photo, press "x" to reject it. The filter you created in the second step should remove it from the grid. It's still in Lightroom (and the collection), it's just hidden by the filter.
When you get bored and want to finish for the night, come out of the smart collection and pull up all the rejected images. (I have a filter for "show rejected" to make this easy)
Either...
a) delete them from LR & disk. They're gone.
b) delete them from LR only. They'll remain on disk and you can re-add them in the future if you're worried about deleting something now you might want later. If you do this, it's worth giving all the images a "rejected" keyword and saving it back to the raw file/jpeg (CTRL+S) before deleting from the catalogue. That way, if you re-import them again, you can quickly find them with a filter against the "rejected" keyword.
Once this is done, you're left with a smart collection containing all the photos you haven't looked at yet. Your "keepers" will all have a way to identify them, and the ones you rejected will either be flagged as rejected (with the "x" key) or won't be in the catalogue.
This method allows you to do a hundred or so a night, or half a dozen here & there and the smart collection will just track your progress. It makes the job much less daunting.
I used this process for keywording all my images when I decided to do it properly (and was also outfaced by the enormity of it). It allowed me to tackle the job in bite sized chunks and continues today to remind me what I still have to keyword.
e.g.

Damn... it got up to 200...