Help installing Parallels, please!

I am about to install Parallels on my Mac Pro but I am having
some initial problems.

I selected CUSTOM INSTALL because it allows me to specify
how much memory and hard drive space I want to dedicate
to Parallels.

1. It asks how much memory (RAM) i want for my virtual machine.
I want 2GB (I have a 4GB computer). What does this translate to
in MB? I maxxed it out at 1500MB. Is this correct?

2. It asks if I want to CREATE A NEW HARD DISK IMAGE. I tell
it yes, and I am guessing this is correct.

3. SPECIFY SIZE OF VIRTUAL DISK. I want 250GB (I have a 500GB
drive) dedicated to Parallels. What is the MB equivalent?

4. At this point, it will only let me select BRIDGED ETHERNET or
NETWORKING IS NOT REQUIRED. The other two choices are
grayed out. I want to use my Mac ethernet connection for my
Internet and use AIRPORT EXPRESS for my wireless printer. What
should I use here?

5. Next step gives me choice of DEFAULT ADAPTER or a list
of two other adapters + Airport/Wireless adapter. Again, I
connect to the Internet via Ethernet and Airport is used solely
for the wireless printer.

Help would be greatly appreciated!

1. 1500 mb is 1.5 Gb so 2000MB is 2Gb
2. A new hard disk image is correct
3. The MB of 250GB is 250,000MB
4. I think that Bridged Ethernet is the correct choice
5. I am not sure about this one... Sorry

More problems...

I installed Parallels according to EXPRESS INSTALL.

Vista installed fine.

Got as far as installing my Internet Security and Antivirus.

Vista had problems rebooting. It just sat there at the load
screen. So, I went into tools and put in the maximum memory
1500MB.

When I tried to start Parallels I got this message:

"Unable to allocate virtual machine memory!

This error may occur mostly if there is no enough free
disk space available on the physical disk to allocate virtual
machine paging file. Try to clean up the physical disk.
If it doesn't help, try to re-install Parallels desktop."

Can someone kindly instruct me how to max out all
the necessary VIDEO and MEMORY areas effectively if
I want 2GB RAM and 250GB hard drive space for Parallels?

Note: I tried putting 250,000MB in the Hard Disk settings
but it was much too high a setting for Parallels to handle.
It will not let me put in anything above 128,000MB. On
the Memory end, it will not let me go above 1500MB.

Thank You!