JPfm is a java language binding for pismo file mount. SplitFS is made using JPfm. SplitFS can merge hundreds of *.001 type of splits as big as 100TB in size in about 5 seconds. This is possible because it doesn't actually merge the file, it creates a virtual folder and creates a virtual "merge" file inside it.
Windows Server 2008,
||Pismo File Mount 1.54, Java Runtime Environment 1.7