Paul is speaking using the figure of speech called prosopopaeia, assuming the voice of someone who is now dead.
Rom 7:14
For we know that the law is spiritual: but I am carnal, sold under sin.
Rom 7:15
For that which I do I allow not: for what I would/want/will/desire, that do I not; but what I hate, that do I.
Rom 7:16
If then I do that which I would/will/want/desire not, I consent unto the law that
it is good.
Rom 7:17
Now then it is no more I that do it, but sin that dwells in me.
Rom 7:18
For I know that in me (that is, in my flesh,) dwells no good thing: for
to will/want/desire is present with me; but
how to perform that which is good I find not.
Rom 7:20
Now if I do that I would/will/want/desire not, it is no more I that do it, but sin that dwells in me.
Rom 7:21
I find then a law, that, when I would/will/want/desire do good, evil is present with me.
Rom 7:22
For
I delight in the law of God after the inward man:
Rom 7:23
But I see another law in my members, warring against
the law of my mind, and bringing me
into captivity to the law of sin which is in my members.
Rom 7:24
O wretched man that I am! who shall deliver me from
the body of this death?
Rom 7:25
I thank God through Jesus Christ our Lord. So then
with the mind I myself serve the law of God; but
with the flesh the law of sin.
Before being purchased from the power of sin and being brought to life by faith in Christ, Paul was sold under sin, brought into cpativity to the law of sin which was in his members, being killed by his body and with the flesh serving sin. Nevertheless, in that state he was capable of wanting in his mind to obey the law of Moses, to agree that that law was good; to will/want/desire to do good was present in His mind; he delighted in the law of God in his inward man, and was able with his mind to serve the law of God.
Does that sound like a man whose will was not free to desire good, and was only bound to desiring evil?