Bad blocks in hard disk - S.M.A.R.T - report

Question

I have a DELL PRECISION M4400 running Windows 7 Professional.
Recently, the laptop started freezing and would go to sleep and would not be able to wake up unless a hard reset was given.
I downloaded and ran the DELL diagnostics from the DELL website which indicated a HDD failure. It was recommended to replace the HDD. I got the following (truncated) report (SMART) for the 320GB HDD.

WDC WD3200BEKT-75PVMT0-WD-WXL1A91U2336-TEST.mht
HDDScan Drive Test Report 
Model: WDC WD3200BEKT-75PVMT0
Firmware: 01.01A01
Serial: WD-WXL1A91U2336
LBA: 625142448

Report By: HDDScan for Windows version 3.3
Report Date: 8/21/2015 1:08:33 AM

Open Disk
Test : RD-Read

Executing
Block start at 2428416 time 55ms
.
.
Block start at 14633472 time 51ms
Bad block found, start LBA : 19194880
Block start at 26177024 time 261ms
.
.
Block start at 41292800 time 58ms
Bad block found, start LBA : 46550528
Block start at 46551296 time 73ms
Block start at 46551552 time 74ms
Block start at 46554624 time 64ms
Bad block found, start LBA : 46574592
Bad block found, start LBA : 46576384
Block start at 46576640 time 100ms
.
Block start at 46577920 time 112ms
Bad block found, start LBA : 46578432
Bad block found, start LBA : 46582272
Block start at 46582528 time 273ms
Block start at 46583040 time 64ms
Bad block found, start LBA : 46586624
Block start at 46590720 time 84ms
.
.
Block start at 46671104 time 59ms
Bad block found, start LBA : 46672128
Bad block found, start LBA : 46675968
Block start at 46676224 time 154ms
.
.
Block start at 618832128 time 107ms

From the report I understand that, only a portion of the hard drive has bad sectors only from the beginning (Bad block found, start LBA : 46675968 is the last one)

I'm planning to allocate till this as un-partitioned space and not use it. The question is how many GB's should I make as un-partitioned space so that I can continue to use my laptop.

I tried researching the internet for the meaning of LBA and its co-relation to hard drive size - all in vain. The Wiki page on LBA is of very little use in this context.

(Note: I do not mind losing data in case if the HDD fails suddenly. Just want to make the maximum out of this HDD)

Edit

From here, I understand that this formula which converts LBA to GB:

(LBA*512) / (1024^3)

By this formula: 46675968 / (1024^3) = 22.25GB - which I'd roundup as 25GB

Would this be correct?

Answer 1

You don't need to leave unpartitioned space.

While in OS:

Use Windows Full format. Uncheck the "Quick Format" checkbox during formatting a partition in windows.

While Installing Windows:

Format through command line diskpart. Before clicking install in Windows setup, enter shift + F10 and command prompt opens. Enter the command diskpart and it opens diskpart. Then enter commands..

list disk - lists available disks numbered from 0.

select disk 0 - selects disk 0 or 1st hard disk.

list partition - lists available partitions in disk 0.

select partition 0 - Selects the first partition in disk 0.

format fs=ntfs - Formats with file system ntfs. Here "quick" argument is omitted to force a full format.

Then close command prompt and install windows.

Such Full Format will mark all the bad blocks and will not use them.

But these bad blocks are going to increase over time rapidly and the disk is going to fail sometime later. Backup your data.