I have a SONY DRU510A and I'm having problems burning files close to 700mb on a 700mb SONY CD-R. I tried a data disk with an .mpg file of 697mb and Nero tells me there isn't enough space. And I just now tried to burn an iso that was 699mb and again it says not enough space. I made sure discs were blank, I don't understand why nero won't let me burn it. Should I try another program?

There has to be space on the disk for lead-in and close-out data. The amount varies according to what format you are burning, but allow 5 to 10 MB at least. Some burning programs have an "overburn" feature but I have never used them.
Arnie

This article outlines how to use Nero to burn to 800 mb disks but same method applies to 700 mb disk overburning.

2 things are required to burn 800 MB (90 minute) disks:

1: Recording software that supports overburning (Nero Burning Rom DOES)
2: A cd burner that supports overburning. (if it doesn't then firmware update is the only solution... only if the firmware provides this feature)

Here's how I did it using Nero Burning Rom recording software:

Step 1: Install Nero Burning Rom and ensure it's working properly with your recorder.

Step 2: Verify whether the CD-Recorder you're using supports overburning. To do this, open Nero and choose RECORDER menu. In this dialog box, see the drive information by selecting your CD-RECORDER (highlight [your particular drive] by clicking once). Here you can check to see if your recorder support's over burn or not. In lower portion of dialog box, you will see the word: "Overburn". Out beside it you will see one of two listings: 1: "Supported" or 2: "Not Supported"

If your drive supports overburning proceed to step 3. If it doesn't, STOP and check to see if you can find firmware that will update and provide "overburning" feature.

Step 3: This step will show you how to check the capacity of the CD-R disc you're using for recording.
Go go Recorder menu and select "MEDIUM INFO". In this dialog box, you will see that total capacity is: 00:00:00 (0 MB) and "available capacity" 10:00:00 (88 MB). This is absolutely ok for using 90 minute (800 MB) CD-R. Step #4 will explain how to check amount of data (source length).

Step 4: Go to FILE menu and select WRITE CD. (If you have not made a compilation earlier then please make it first by selecting "NEW COMPILATION). In this dialog box, select "INFO". This will give you information about the exact total of data. Just make sure that this amount should always be less than the "Maximum CD Length", which we will select in "EXPERT FEATURE".
Always use "disk at-once" method only while writing an over sized CD-R.

Step 5: Now, the most important setting about EXPERT FEATURE over burn Maximum CD length... Please do the following:

Go to FILE menu, select PREFERENCES, and then select EXPERT FEATURE. This is the main area where you have to select ENABLE OVER BURN and enter "90 min 2 sec 0 frame", then click OK. This will allow you to make over size burning.
After making these settings, start WRITING. When you click the WRITE button, it will ask for confirmation about "OVERBURNING" by showing another window. You have to click the "WRITE OVER BURN CD" button on lower right of dialog box.;)