i currently have an old hardtail

(here are the specs: https://www.ibexbikes.com/Bikes/2003/...450-Specs.html ).

i planned to singletrack with it but mostly use it in urban places.

what would you swap and replace to make this more road / long distance friendly?

get a rigid fork? (it currently has rock shox judy fork which is a waste of energy for flat pavement)

this is a entry level bike so would it be cheaper to just buy a road bike?

if not, what would you change first?

I would put some slicks on it.

** 2nd on road slicks, run them narrower, 1.5", at higher pressure.

** Rigid front fork, like you said

** Swap out the front crankset from the 44/32/22 to something more road oriented, say 50/39/30 or so.

Since it's entry level you don't need high end parts so you should be able to make these changes for $100 tops +/- a few bucks.

How long is your commute? Most people don't need anything super special for commuting, any bike will do.

Road tires
Rigid fork (although not all that necessary and a susp.fork may help with potholes)
Fenders (not only for rain, but when ride over fresh dog poo... you get the picture)
Rear rack (so you can carry stuff in a rackbag or pannier instead of a sweaty backpack)
Lights

I wouldn't bother replacing the fork; you're not going to lose that much efficiency with a short-travel front suspension. Don't replace the crankset unless you can spin out (pedal faster than 100 rpm) in your top gear on flat pavement. Just put slick tires on it like others have said, and save your money to buy a more road-worthy bike.

Can you lock the fork out? A lot of them can be adjusted for more or less squishiness, so you might be able to get pretty close to a rigid fork without spending much.

I'd definitely put skinny, slick tires on it, though. You can get some with a little bit of tread, and still take gravel and dirt, but have tires that are really more optimized for doing most of your riding on pavement.

And clipless pedals turn out to be a big help.

I'll take a different approach. Purchase a road bike. You can modify the hardtail, and all you will have is a modified hardtail. Take those dollars, find a good used road bike and you will now have a bike for the urban/commute portion of your riding, and a singletrack rig when the feeling strikes.

buy some new tires....slick and with puncture protection... try to lock your fork...ride ride, untill you cant bare the urge to buy a better bike

One of my bike is a hardtail mtb much like yours. I've so far switched out the knobbies for 1.5" Kenda Kwests. They make a world of difference for paved road riding. I've also swapped the 42t crankset for a 48t crankset from my wife's bike. She'll never need use that.
The result is a comfortable hybrid. I kept the front suspension because part of my commute entails unpaved MUPs. It helps absorb road undulations.
In terms of speed, while my other roadbike will be faster on flats, but on my 15km commute, the times are negligible. Where my road bike rocks on the paved flats and climbs, the hardtail mtb is faster on the unpaved section. Also I find the hardtail more comfortable overall.
Therefore my suggestion is that get skinnier tires and leave the front suspension alone.

thank you for the great replies. you guys rock.