The command is partnew (not partnow).
If the file extents of the file (hd0,0)/disk.raw (from blocklist command) is (hd0,0)5052+201600 you need to operate as follows.
The output of blocklist is:
partition is (hd0,0)
offset is 5052
length is 201600
Now you need to ADD to <offset> the number of "hidden sectors" or "sectors before" in the image (or if you prefer the offset to the PBR inside the image) and to SUBTRACT from <length> the same.
In the case of 63 "sectors before" (which is the default if the image was partitioned under DOS) you will have:
You can verify that you got the right offset by running the command:
cat --hex (hd0,0)5115+1
that should show the PBR, beginning with an EB3C90 jump, and ending with 55AA.
If you run:
cat --hex --length=32 (hd0,0)5115+1
you should see the first two 16-byte rows of the PBR, of which the last four bytes are the "hidden sectors" or "sectors before", normally "3F 00 00 00"= 0x0000003F=0x3F=63
Then you ran the partnew command, which syntax is:
partnew (<partition>) <parttype> <begin> <length>
partnew (<partition>) <parttype> <contiguous extent>
partition is (hd0,1) , i.e. second slot in the partition table of first disk
parttype is 0x06
begin is the partition and the new offset, i.e. (hd0,0)5115
length is the new length 201537
(hd0,0)5115+201537 is the contiguous extent
the command line that becomes:
partnew (hd0,1) 0x06 (hd0,0)5115+201537
The blinking cursor is typical of an issue with the bootsector/wrong offset, unless you made a typo in the above post, you have made some wrong calculations and used a wrong offset, try again.
It is also possible that during your attempts some field/byte in the bootsector was accidentally changed.
Since you had the image working with --mem mapping, try it again as follows:
map --mem (hd0,0)/disk.raw (hd0)